Simplification of combined inter-intra prediction

ABSTRACT

Techniques for implementing video processing techniques are described. In one example implementation, a method of video processing includes determining, for a conversion between a current block of a video coded using a combined inter and intra prediction (CIIP) coding technique and a bitstream representation of the video, an intra-prediction mode of the current block independently from an intra-prediction mode of a neighboring block. The CIIP coding technique uses an intermedia inter prediction value and an intermedia intra prediction value to derive a final prediction value of the current block. The method also includes performing the conversion based on the determining.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2019/117508, filed on Nov. 12, 2019, which claims the priority toand benefits of International Patent Application No. PCT/CN2018/115042,filed on Nov. 12, 2018, International Patent Application No.PCT/CN2018/115840, filed on Nov. 16, 2018, International PatentApplication No. PCT/CN2019/070060, filed on Jan. 2, 2019, InternationalPatent Application No. PCT/CN2019/070549, filed on Jan. 6, 2019,International Patent Application No. PCT/CN2019/075546, filed on Feb.20, 2019, International Patent Application No. PCT/CN2019/075858, filedon Feb. 22, 2019, International Patent Application No.PCT/CN2019/077179, filed on Mar. 6, 2019, International PatentApplication No. PCT/CN2019/078939, filed on Mar. 20, 2019, andInternational Patent Application No. PCT/CN2019/079397, filed on Mar.24, 2019. All the aforementioned patent applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

This patent document relates to image and video coding and decoding.

BACKGROUND

Digital video accounts for the largest bandwidth use on the internet andother digital communication networks. As the number of connected userdevices capable of receiving and displaying video increases, it isexpected that the bandwidth demand for digital video usage will continueto grow

SUMMARY

The present document discloses various video processing techniques thatcan be used by video encoders and decoders during encoding and decodingoperations.

In one example aspect, a method of video processing is disclosed. Themethod includes determining, for a conversion between a current block ofa video and a bitstream representation of the video using an affinecoding tool, that a first motion vector of a sub-block of the currentblock and a second motion vector that is a representative motion vectorfor the current block comply with a size constraint. The method alsoincludes performing the conversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video and a bitstream representation of the video, an affinemodel that comprises six parameters. The affine model is inherited fromaffine coding information of a neighboring block of the current block.The method also includes performing the conversion based on the affinemodel.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a block of avideo and a bitstream representation of the video, whether abi-prediction coding technique is applicable to the block based on asize of the block having a width W and a height H, W and H beingpositive integers. The method also includes performing the conversionaccording to the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a block of avideo and a bitstream representation of the video, whether a coding treesplit process is applicable to the block based on a size of a sub-blockthat is a child coding unit of the block according to the coding treesplit process. The sub-block has a width W and a height H, W and H beingpositive integers. The method also includes performing the conversionaccording to the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video and a bitstream representation of the video, whether anindex of a bi-prediction with coding unit level weight (BCW) coding modeis derived based on a rule with respect to a position of the currentblock. In the BCW coding mode, a weight set including multiple weightsis used to generate bi-prediction values of the current block. Themethod also includes performing the conversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video coded using a combined inter and intra prediction(CIIP) coding technique and a bitstream representation of the video, anintra-prediction mode of the current block independently from anintra-prediction mode of a neighboring block. The CIIP coding techniqueuses an intermediate inter prediction value and an intermediate intraprediction value to derive a final prediction value of the currentblock. The method also includes performing the conversion based on thedetermining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video coded using a combined inter and intra prediction(CIIP) coding technique and a bitstream representation of the video, anintra-prediction mode of the current block according to a firstintra-prediction mode of a first neighboring block and a secondintra-prediction mode of a second neighboring block. The firstneighboring block is coded using an intra-prediction coding techniqueand the second neighboring block is coded using the CIIP codingtechnique. The first intra-prediction mode is given a priority differentthan the second intra-prediction mode. The CIIP coding technique uses anintermediate inter prediction value and an intermediate intra predictionvalue to derive a final prediction value of the current block. Themethod also includes performing the conversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video and a bitstream representation of the video, whether acombined inter and intra prediction (CIIP) process is applicable to acolor component of the current block based on a size of the currentblock. The CIIP coding technique uses an intermediate inter predictionvalue and an intermediate intra prediction value to derive a finalprediction value of the current block. The method also includesperforming the conversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video and a bitstream representation of the video, whether acombined inter and intra prediction (CIIP) coding technique is to beapplied to the current block based on a characteristic of the currentblock. The CIIP coding technique uses an intermediate inter predictionvalue and an intermediate intra prediction value to derive a finalprediction value of the current block. The method also includesperforming the conversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video and a bitstream representation of the video, whether acoding tool is to be disabled for the current block based on whether thecurrent block is coded with a combined inter and intra prediction (CIIP)coding technique. The coding tool comprises at least one of: aBi-Directional Optical Flow (BDOF), an Overlapped Block MotionCompensation (OBMC), or a decoder-side motion vector refinement process(DMVR). The method also includes performing the conversion based on thedetermining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a block of avideo and a bitstream representation of the video, a first precision P1used for motion vectors for spatial motion prediction and a secondprecision P2 used for motion vectors for temporal motion prediction. P1and/or P2 are fractions, and neither P1 nor P2 is signaled in thebitstream representation. The method also includes performing theconversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a block of avideo and a bitstream representation of the video, a motion vector (MVx,MVy) with a precision (Px, Py). Px is associated with MVx and Py isassociated with MVy. MVx and MVy are stored as integers each having Nbits, and MinX≤MVx≤MaxX and MinY≤MVy≤MaxY, MinX, MaxX, MinY, and MaxYbeing real numbers. The method also includes performing the conversionbased on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video and a bitstream representation of the video, whether ashared merge list is applicable to the current block according to acoding mode of the current block. The method also includes performingthe conversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of video having a W×H size and a bitstream representation of thevideo, a second block of a dimension (W+N−1)×(H+N−1) for motioncompensation during the conversion. The second block is determined basedon a reference block of a dimension (W+N−1−PW)×(H+N−1−PH). N representsa filter size, W, H, N, PW and PH are non-negative integers. PW and PHare not both equal to 0. The method also includes performing theconversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion between a currentblock of a video having a W×H size and a bitstream representation of thevideo, a second block of a dimension (W+N−1)×(H+N−1) for motioncompensation during the conversion. W, H are non-negative integers, andN are non-negative integers and based on a filter size. During theconversion, a refined motion vector is determined based on a multi-pointsearch according to a motion vector refinement operation on an originalmotion vector, and pixels long boundaries of the reference block aredetermined by repeating one or more non-boundary pixels. The method alsoincludes performing the conversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining, for a conversion of a block of a videothat is coded using a Combined Inter-Intra Prediction (CIIP) codingtechnique and a bitstream representation of the video, a predictionvalue at a position in the block based on a weighted sum of an interprediction value and an intra prediction value at the position. Theweighted sum is based on adding an offset to an initial sum obtainedbased on the inter prediction value and the intra prediction value, andthe offset is added prior to a right-shift operation performed todetermine the weighted sum. The method also includes performing theconversion based on the determining.

In another example aspect, a method of video processing is disclosed.The method includes determining a size restriction between arepresentative motion vector of a current video block that is affinecoded and motion vectors of sub-blocks of the current video block andperforming, by using the size restriction, a conversion between abitstream representation and pixel values of the current video block orthe subblocks.

In another example aspect, another method of video processing isdisclosed. The method includes determining for a current video blockthat is affine coded, one or more sub-blocks of the current video block,wherein each sub-block has a size of M×N pixels, where M and N aremultiples of 2 or 4, conforming motion vectors of the sub-blocks to asize restriction, and performing, conditionally based on a trigger, byusing the size restriction, a conversion between a bitstreamrepresentation and pixel values of the current video block.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining that a current video blocksatisfies a size condition, and performing, based on the determining, aconversion between a bitstream representation and pixel values of thecurrent video block by excluding bi-prediction encoding mode for thecurrent video block.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining that a current video blocksatisfies a size condition and performing, based on the determining, aconversion between a bitstream representation and pixel values of thecurrent video block wherein an inter prediction mode is signaled in thebitstream representation according to the size condition.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining that a current video blocksatisfies a size condition, and performing, based on the determining, aconversion between a bitstream representation and pixel values of thecurrent video block wherein a generation of merge candidate list duringthe conversion is dependent on the size condition.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining that a child coding unit of acurrent video block satisfies a size condition, and performing, based onthe determining, a conversion between a bitstream representation andpixel values of the current video block, wherein a coding tree splittingprocess used to generate the child coding unit is dependent on the sizecondition.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining, a weight index for ageneralized bi-prediction (GBi) process for a current video block basedon a position of the current video block and performing a conversionbetween the current video block and a bitstream representation thereofusing the weight index to implement the GBi process.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining that a current video block iscoded as an intra-inter prediction (IIP) coded block and performing aconversion between the current video block and a bitstreamrepresentation thereof using a simplification rule for determining anintra-prediction mode or a most probable mode (MPM) for the currentvideo block.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining that a current video blockmeets a simplification criterion and performing a conversion between thecurrent video block and a bitstream representation by disabling use ofinter-intra prediction mode for the conversion or by disablingadditional coding tools used for the conversion.

In yet another example aspect, another method of video processing isdisclosed. The method includes performing a conversion between a currentvideo block and a bitstream representation for the current video blockusing a motion vector based encoding process wherein (a) a precision P1is used for storing spatial motion prediction results and a precision P2is used for storing temporal motion prediction results during theconversion process, wherein P1 and P2 are fractional numbers or (b) aprecision Px is used for storing x-motion vectors and a precision Py isused for storing y-motion vectors, wherein Px and Py are fractionalnumbers.

In yet another example aspect, another method of video processing isdisclosed. The method includes interpolating, a small sub-block of W1×H1size within a large sub-block of W2×H2 size of a current video block byfetching a (W2+N−1−PW)*(H2+N−1−PH) block, pixel padding the fetchedblock, performing boundary pixel repeating on the pixel padded block andobtaining pixel values of the small sub-block, wherein W1, W2, H1, H2,and PW and PH are integers and performing a conversion between thecurrent video block and a bitstream representation of the current videoblock using the interpolated pixel values of the small sub-block.

In another example aspect, another method of video processing isdisclosed. The method includes performing, during a conversion of acurrent video block of W×H dimension and a bitstream representation ofthe current video block, a motion compensation operation by fetching(W+N−1−PW)*(W+N−1−PH) reference pixels and padding reference pixelsoutsize the fetched reference pixels during the motion compensationoperation and performing a conversion between the current video blockand a bitstream representation of the current video block using a resultof the motion compensation operation, where W, H, N, PW and PH areintegers.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining, based on a size of a currentvideo block, that bi-prediction or uni-prediction of the current videoblock is disallowed, and performing, based on the determining, aconversion between a bitstream representation and pixel values of thecurrent video block by disabling bi-prediction or uni-prediction mode.

In yet another example aspect, another method of video processing isdisclosed. The method includes determining, based on a size of a currentvideo block, that bi-prediction or uni-prediction of the current videoblock is disallowed, and performing, based on the determining, aconversion between a bitstream representation and pixel values of thecurrent video block by disabling bi-prediction or uni-prediction mode.

In yet another example aspect, a video encoder apparatus is disclosed.The video encoder comprises a processor configured to implementabove-described methods.

In yet another example aspect, a video encoder apparatus is disclosed.The video encoder comprises a processor configured to implementabove-described methods.

In yet another example aspect, a computer readable medium having codestored thereon is disclose. The code embodies one of the methodsdescribed herein in the form of processor-executable code.

These, and other, features are described throughout the presentdocument.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an example of sub-block based prediction.

FIG. 2A shows a 4-parameter affine model.

FIG. 2B shows a 6-parameter affine model.

FIG. 3 shows an example of an affine motion vector field per sub-block.

FIG. 4A show an example of candidates for AF_MERGE.

FIG. 4B show another example of candidates for AF_MERGE.

FIG. 5 shows candidate positions for affine merge mode.

FIG. 6 shows an example of a constrained sub-block motion vector for acoding unit (CU) of an affine mode.

FIG. 7A shows an example of a 135 degree parttion of splitting a CU intotwo triangular prediction units.

FIG. 7B shows an example of a 45 degree splitting pattern of splitting aCU into two triangular prediction units.

FIG. 8 shows examples of positions of neighboring blocks.

FIG. 9 shows an example of repeat boundary pixels of a reference blockbefore interpolation.

FIG. 10 shows an example of a coding tree unit (CTU) and CTU (region)lines. Shaded CTUs (regions) are in one CUT (region) line, Un-shadedCTUs (regions) are in the other CUT (region) line.

FIG. 11 is a block diagram of an example of a hardware platform forimplementing a video decoder or video encoder apparatus describedherein.

FIG. 12 is a flowchart for an example method of video processing.

FIG. 13 shows an example of a motion vector difference MVD (0,1)mirrored between list 0 and liste 1 in DMVR.

FIG. 14 shows example MVs that may be checked in one iteration.

FIG. 15 shows required reference samples and boundary padded forcalculations.

FIG. 16 is a block diagram of an example video processing system inwhich disclosed techniques may be implemented.

FIG. 17 is a flowchart represent of a method for video processing inaccordance with the present disclosure.

FIG. 18 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 19 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 20 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 21 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 22 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 23 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 24 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 25 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 26 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 27 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 28 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 29 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 30 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 31 is a flowchart represent of another method for video processingin accordance with the present disclosure.

FIG. 32 is a flowchart represent of yet another method for videoprocessing in accordance with the present disclosure.

DETAILED DESCRIPTION

Section headings are used in the present document for ease ofunderstanding and do not limit the applicability of techniques andembodiments disclosed in each section only to that section.

1. Summary

This patent document is related to video/image coding technologies.Specifically, it is related to reducing bandwidth and line buffers ofseveral coding tools in video/image coding. It may be applied to theexisting video coding standards like HEVC, or the standard (VersatileVideo Coding) to be finalized. It may be also applicable to futurevideo/image coding standards or video/image codec.

2. Background

Video coding standards have evolved primarily through the development ofthe well-known ITU-T and ISO/IEC standards. The ITU-T produced H.261 andH.263, ISO/IEC produced MPEG-1 and MPEG-4 Visual, and the twoorganizations jointly produced the H.262/MPEG-2 Video and H.264/MPEG-4Advanced Video Coding (AVC) and H.265/HEVC standards. Since H.262, thevideo coding standards are based on the hybrid video coding structurewherein temporal prediction plus transform coding are utilized. Toexplore the future video coding technologies beyond HEVC, Joint VideoExploration Team (JVET) was founded by VCEG and MPEG jointly in 2015.Since then, many new methods have been adopted by JVET and put into thereference software named Joint Exploration Model (JEM). In April 2018,the Joint Video Expert Team (JVET) between VCEG (Q6/16) and ISO/IEC JTC1SC29/WG11 (MPEG) was created to work on the VVC standard targeting at50% bitrate reduction compared to HEVC.

2.1 Inter Prediction in HEVC/VVC

Interpolation Filters

In HEVC, luma sub-samples are generated by 8-tap interpolation filtersand chroma sub-samples are generated by 4-tap interpolation filters.

The filters are separable in the two dimensions. Samples are filteredhorizontally first then vertically.

2.2 Sub-Block Based Prediction Technology

Sub-block based prediction is first introduced into the video codingstandard by HEVC Annex I (3D-HEVC). With sub-block based prediction, ablock, such as a Coding Unit (CU) or a Prediction Unit (PU), is dividedinto several non-overlapped sub-blocks. Different sub-block may beassigned different motion information, such as reference index or MotionVector (MV), and Motion Compensation (MC) is performed individually foreach sub-block. FIG. 1 demonstrates the concept of sub-block basedprediction.

To explore the future video coding technologies beyond HEVC, Joint VideoExploration Team (JVET) was founded by VCEG and MPEG jointly in 2015.Since then, many new methods have been adopted by JVET and put into thereference software named Joint Exploration Model (JEM).

In JEM, sub-block based prediction is adopted in several coding tools,such as affine prediction, Alternative temporal motion vector prediction(ATMVP), spatial-temporal motion vector prediction (STMVP),Bi-directional Optical flow (BIO) and Frame-Rate Up Conversion (FRUC).Affine prediction has also been adopted into VVC.

2.3 Affine Prediction

In HEVC, only translation motion model is applied for motioncompensation prediction (MCP). While in the real world, there are manykinds of motion, e.g. zoom in/out, rotation, perspective motions and theother irregular motions. In the VVC, a simplified affine transformmotion compensation prediction is applied. As shown FIG. 2A-2B, theaffine motion field of the block is described by two (in the 4-parameteraffine model) or three (in the 6-parameter affine model) control pointmotion vectors.

The motion vector field (MVF) of a block is described by the followingequations with the 4-parameter affine model (wherein the 4-parameter aredefined as the variables a, b, e and f) in Eq. (1) and 6-parameteraffine model (wherein the 4-parameter are defined as the variables a, b,c, d, e and f) in Eq. (2) respectively:

$\begin{matrix}{\mspace{650mu}{{Eq}.\mspace{14mu}(1)}} \\\left\{ \begin{matrix}{{{mv}^{h}\left( {x,y} \right)} = {{{ax} - {by} + e} = {{\frac{\left( {{mv}_{1}^{h} - {mv}_{0}^{h}} \right)}{w}x} - {\frac{\left( {{mv}_{1}^{v} - {mv}_{0}^{v}} \right)}{w}y} + {mv}_{0}^{h}}}} \\{{{mv}^{v}\left( {x,y} \right)} = {{{bx} + {ay} + f} = {{\frac{\left( {{mv}_{1}^{v} - {mv}_{0}^{v}} \right)}{w}x} + {\frac{\left( {{mv}_{1}^{h} - {mv}_{0}^{h}} \right)}{w}y} + {mv}_{0}^{v}}}}\end{matrix} \right. \\{\mspace{650mu}{{Eq}.\mspace{14mu}(2)}} \\\left\{ \begin{matrix}{{{mv}^{h}\left( {x,y} \right)} = {{{ax} + {cy} + e} = {{\frac{\left( {{mv}_{1}^{h} - {mv}_{0}^{h}} \right)}{w}x} + {\frac{\left( {{mv}_{2}^{h} - {mv}_{0}^{h}} \right)}{h}y} + {mv}_{0}^{h}}}} \\{{{mv}^{v}\left( {x,y} \right)} = {{{bx} + {dy} + f} = {{\frac{\left( {{mv}_{1}^{v} - {mv}_{0}^{v}} \right)}{w}x} + {\frac{\left( {{mv}_{2}^{v} - {mv}_{0}^{v}} \right)}{h}y} + {mv}_{0}^{v}}}}\end{matrix} \right.\end{matrix}$

where (mv^(h) ₀, mv^(h) ₀) is motion vector of the top-left cornercontrol point, and (mv^(h) ₁, mv^(h) ₁) is motion vector of thetop-right corner control point and (mv^(h) ₂, mv^(h) ₂) is motion vectorof the bottom-left corner control point, all of the three motion vectorsare called control point motion vectors (CPMV), (x, y) represents thecoordinate of a representative point relative to the top-left samplewithin current block. The CP motion vectors may be signaled (like in theaffine AMVP mode) or derived on-the-fly (like in the affine merge mode).w and h are the width and height of the current block. In practice, thedivision is implemented by right-shift with a rounding operation. InVTM, the representative point is defined to be the center position of asub-block, e.g., when the coordinate of the left-top corner of asub-block relative to the top-left sample within current block is (xs,ys), the coordinate of the representative point is defined to be (xs+2,ys+2).

In a division-free design, Eq. (1) and Eq. (2) are implemented as

$\begin{matrix}\left\{ \begin{matrix}{{iDMvHorX} = {\left( {{mv}_{1}^{h} - {mv}_{0}^{h}} \right) ⪡ \left( {S - {\log\; 2(w)}} \right)}} \\{{iDMvHorY} = {\left( {{mv}_{1}^{v} - {mv}_{0}^{v}} \right) ⪡ \left( {S - {\log\; 2(w)}} \right)}}\end{matrix} \right. & {{Eq}.\mspace{14mu}(3)}\end{matrix}$

For the 4-parameter affine model shown in (1):

$\begin{matrix}\left\{ \begin{matrix}{{iDMvVerX} = {- {iDMvHorY}}} \\{{iDMvVerY} = {iDMvHorX}}\end{matrix} \right. & {{Eq}.\mspace{14mu}(4)}\end{matrix}$

For the 6-parameter affine model shown in (2):

$\begin{matrix}\left\{ \begin{matrix}{{iDMvVerX} = \left( {{{mv}_{2}^{h} - {mv}_{0}^{h}} ⪡ \left( {S - {\log\; 2(h)}} \right)} \right.} \\{{iDMvVerY} = {\left( {{mv}_{2}^{v} - {mv}_{0}^{v}} \right) ⪡ \left( {S - {\log\; 2(h)}} \right)}}\end{matrix} \right. & {{Eq}.\mspace{14mu}(5)}\end{matrix}$

Finally,

$\begin{matrix}\left\{ \begin{matrix}{\;\begin{matrix}{{{mv}^{h}\left( {x,y} \right)} = {{Normalize}\left( {{{iDMvHorX}\;\bullet\; x} +} \right.}} \\\left. {{{{iDMvVerX}\;\bullet\; y} + \left( {{mv}_{0}^{h} ⪡ S} \right)},S} \right)\end{matrix}} \\\begin{matrix}{{{mv}^{v}\left( {x,y} \right)} = {{Normalize}\left( {{{iDMvHorY}\;\bullet\; x} +} \right.}} \\\left. {{{{iDMvVerY}\;\bullet\; y} + \left( {{mv}_{0}^{v} ⪡ S} \right)},S} \right)\end{matrix}\end{matrix} \right. & {{Eq}.\mspace{14mu}(6)} \\{{{Normalize}\left( {Z,S} \right)} = \left\{ {{\begin{matrix}{\left( {Z + {Off}} \right) ⪢ S} & {{{if}\mspace{14mu} Z} \geq 0} \\{- \left( {\left( {{- Z} + {Off}} \right) ⪢ S} \right)} & {Otherwise}\end{matrix}{Off}} = {1 ⪡ \left( {S - 1} \right)}} \right.} & {{Eq}.\mspace{14mu}(7)}\end{matrix}$

where S represents the calculation precision. e.g. in VVC, S=7. In VVC,the MV used in MC for a sub-block with the top-left sample at (xs, ys)is calculated by Eq. (6) with x=xs+2 and y=ys+2.

To derive motion vector of each 4×4 sub-block, the motion vector of thecenter sample of each sub-block, as shown in FIG. 3, is calculatedaccording to Eq. (1) or Eq. (2), and rounded to 1/16 fraction accuracy.Then the motion compensation interpolation filters are applied togenerate the prediction of each sub-block with derived motion vector.

Affine model can be inherited from spatial neighboring affine-codedblock such as left, above, above right, left bottom and above leftneighboring block as shown in FIG. 4A. For example, if the neighbourleft bottom block A in FIG. 4A is coded in affine mode as denoted by A0in FIG. 4B, the Control Point (CP) motion vectors mv₀ ^(N), mv₁ ^(N) andmv₂ ^(N) of the top left corner, above right corner and left bottomcorner of the neighboring CU/PU which contains the block A are fetched.And the motion vector mv₀ ^(C), mv₁ ^(C) and mv₂ ^(C) (which is onlyused for the 6-parameter affine model) of the top left corner/topright/bottom left on the current CU/PU is calculated based on mv₀ ^(N),mv₁ ^(N) and mv₂ ^(N). It should be noted that in VTM-2.0, sub-block(e.g. 4×4 block in VTM) LT stores mv0, RT stores mv1 if the currentblock is affine coded. If the current block is coded with the6-parameter affine model, LB stores mv2; otherwise (with the 4-parameteraffine model), LB stores mv2′. Other sub-blocks stores the MVs used forMC.

It should be noted that when a CU is coded with affine merge mode, e.g.,in AF_MERGE mode, it gets the first block coded with affine mode fromthe valid neighbour reconstructed blocks. And the selection order forthe candidate block is from left, above, above right, left bottom toabove left as shown FIG. 4A.

The derived CP MVs mv₀ ^(C), mv₁ ^(C) and mv₂ ^(C) of current block canbe used as CP MVs in the affine merge mode. Or they can be used as MVPfor affine inter mode in VVC. It should be noted that for the mergemode, if the current block is coded with affine mode, after deriving CPMVs of current block, the current block may be further split intomultiple sub-blocks and each block will derive its motion informationbased on the derived CP MVs of current block.

2.4 Example Embodiment in JVET

Different from VTM wherein only one affine spatial neighboring block maybe used to derive affine motion for a block. In some embodiments, aseparate list of affine candidates is constructed for the AF_MERGE mode.

1) Insert inherited affine candidates into candidate list

Inherited affine candidate means that the candidate is derived from thevalid neighbor reconstructed block coded with affine mode. As shown inFIG. 5, the scan order for the candidate block is A₁, B₁, B₀, A₀ and B₂.When a block is selected (e.g., A₁), the two-step procedure is applied:

1.a Firstly, use the three corner motion vectors of the CU covering theblock to derive two/three control points of current block.

1.b Based on the control points of current block to derive sub-blockmotion for each sub-block within current block

2) Insert constructed affine candidates

If the number of candidates in affine merge candidate list is less thanMaxNumAffineCand, constructed affine candidates are insert into thecandidate list.

Constructed affine candidate means the candidate is constructed bycombining the neighbor motion information of each control point.

The motion information for the control points is derived firstly fromthe specified spatial neighbors and temporal neighbor shown in FIG. 5.CPk (k=1, 2, 3, 4) represents the k-th control point. A₀, A₁, A₂, B₀,B₁, B₂ and B₃ are spatial positions for predicting CPk (k=1, 2, 3); T istemporal position for predicting CP4.

The coordinates of CP1, CP2, CP3 and CP4 is (0, 0), (W, 0), (H, 0) and(W, H), respectively, where W and H are the width and height of currentblock.

The motion information of each control point is obtained according tothe following priority order:

2.a For CP1, the checking priority is B₂→B₃→A₂. B₂ is used if it isavailable. Otherwise, if B₂ is available, B₃ is used. If both B₂ and B₃are unavailable, A₂ is used. If all the three candidates areunavailable, the motion information of CP1 cannot be obtained.

2.b For CP2, the checking priority is B1→B0;

2.c For CP3, the checking priority is A1→A0;

2.d For CP4, T is used.

Secondly, the combinations of controls points are used to construct themotion model.

Motion vectors of three control points are needed to compute thetransform parameters in 6-parameter affine model. The three controlpoints can be selected from one of the following four combinations({CP1, CP2, CP4}, {CP1, CP2, CP3}, {CP2, CP3, CP4}, {CP1, CP3, CP4}).For example, use CP1, CP2 and CP3 control points to construct6-parameter affine motion model, denoted as Affine (CP1, CP2, CP3).

Motion vectors of two control points are needed to compute the transformparameters in 4-parameter affine model. The two control points can beselected from one of the following six combinations ({CP1, CP4}, {CP2,CP3}, {CP1, CP2}, {CP2, CP4}, {CP1, CP3}, {CP3, CP4}). For example, usethe CP1 and CP2 control points to construct 4-parameter affine motionmodel, denoted as Affine (CP1, CP2).

The combinations of constructed affine candidates are inserted into tocandidate list as following order: {CP1, CP2, CP3}, {CP1, CP2, CP4},{CP1, CP3, CP4}, {CP2, CP3, CP4}, {CP1, CP2}, {CP1, CP3}, {CP2, CP3},{CP1, CP4}, {CP2, CP4}, {CP3, CP4}

3) Insert zero motion vectors

If the number of candidates in affine merge candidate list is less thanMaxNumAffineCand, zero motion vectors are insert into the candidatelist, until the list is full.

2.5 Affine Merge Candidate List 2.5.1 Affine Merge Mode

In the affine merge mode of VTM-2.0.1, only the first available affineneighbour can be used to derive motion information of affine merge mode.In some embodiments, a candidate list for affine merge mode isconstructed by searching valid affine neighbours and combining theneighbor motion information of each control point.

The affine merge candidate list is constructed as following steps:

1) Insert inherited affine candidates

Inherited affine candidate means that the candidate is derived from theaffine motion model of its valid neighbor affine coded block. In thecommon base, as shown FIG. 5, the scan order for the candidate positionsis: A1, B1, B0, A0 and B2.

After a candidate is derived, full pruning process is performed to checkwhether same candidate has been inserted into the list. If a samecandidate exists, the derived candidate is discarded.

2) Insert Constructed Affine Candidates

If the number of candidates in affine merge candidate list is less thanMaxNumAffineCand (set to 5 in this contribution), constructed affinecandidates are inserted into the candidate list. Constructed affinecandidate means the candidate is constructed by combining the neighbormotion information of each control point.

The motion information for the control points is derived firstly fromthe specified spatial neighbors and temporal neighbors. CPk (k=1, 2, 3,4) represents the k-th control point. A0, A1, A2, B0, B1, B2 and B3 arespatial positions for predicting CPk (k=1, 2, 3); T is temporal positionfor predicting CP4.

The coordinates of CP1, CP2, CP3 and CP4 is (0, 0), (W, 0), (H, 0) and(W, H), respectively, where W and H are the width and height of currentblock.

The motion information of each control point is obtained according tothe following priority order:

For CP1, the checking priority is B2→B3→A2. B2 is used if it isavailable. Otherwise, if B2 is available, B3 is used. If both B2 and B3are unavailable, A2 is used. If all the three candidates areunavailable, the motion information of CP1 cannot be obtained.

For CP2, the checking priority is B1→B0.

For CP3, the checking priority is A1→A0.

For CP4, T is used.

Secondly, the combinations of controls points are used to construct anaffine merge candidate.

Motion information of three control points are needed to construct a6-parameter affine candidate. The three control points can be selectedfrom one of the following four combinations ({CP1, CP2, CP4}, {CP1, CP2,CP3}, {CP2, CP3, CP4}, {CP1, CP3, CP4}). Combinations {CP1, CP2, CP3},{CP2, CP3, CP4}, {CP1, CP3, CP4} will be converted to a 6-parametermotion model represented by top-left, top-right and bottom-left controlpoints.

Motion information of two control points are needed to construct a4-parameter affine candidate. The two control points can be selectedfrom one of the following six combinations ({CP1, CP4}, {CP2, CP3},{CP1, CP2}, {CP2, CP4}, {CP1, CP3}, {CP3, CP4}). Combinations {CP1,CP4}, {CP2, CP3}, {CP2, CP4}, {CP1, CP3}, {CP3, CP4} will be convertedto a 4-parameter motion model represented by top-left and top-rightcontrol points.

The combinations of constructed affine candidates are inserted into tocandidate list as following order: {CP1, CP2, CP3}, {CP1, CP2, CP4},{CP1, CP3, CP4}, {CP2, CP3, CP4}, {CP1, CP2}, {CP1, CP3}, {CP2, CP3},{CP1, CP4}, {CP2, CP4}, {CP3, CP4}

For reference list X (X being 0 or 1) of a combination, the referenceindex with highest usage ratio in the control points is selected as thereference index of list X, and motion vectors point to differencereference picture will be scaled.

After a candidate is derived, full pruning process is performed to checkwhether same candidate has been inserted into the list. If a samecandidate exists, the derived candidate is discarded.

3) Padding with Zero Motion Vectors

If the number of candidates in affine merge candidate list is less than5, zero motion vectors with zero reference indices are insert into thecandidate list, until the list is full.

2.5.2 Example Affine Merge Mode

In some embodiments, the affine merge mode can be simplified as follows:

1) The pruning process for inherited affine candidates is simplified bycomparing the coding units covering the neighboring positions, insteadof comparing the derived affine candidates in VTM-2.0.1. Up to 2inherited affine candidates are inserted into affine merge list. Thepruning process for constructed affine candidates is totally removed.

2) The MV scaling operation in constructed affine candidate is removed.If the reference indices of control points are different, theconstructed motion model is discarded.

3) The number of constructed affine candidates is reduced from 10 to 6.

4) In some embodiments, other merge candidates with sub-block predictionsuch as ATMVP is also put into the affine merge candidate list. In thatcase, the affine merge candidate list may be renamed with some othernames such as sub-block merge candidate list.

2.6 Example Control Point MV Offset for Affine Merge Mode

New Affine merge candidates are generated based on the CPMVs offsets ofthe first Affine merge candidate. If the first Affine merge candidateenables 4-parameter Affine model, then 2 CPMVs for each new Affine mergecandidate are derived by offsetting 2 CPMVs of the first Affine mergecandidate; Otherwise (6-parameter Affine model enabled), then 3 CPMVsfor each new Affine merge candidate are derived by offsetting 3 CPMVs ofthe first Affine merge candidate. In Uni-prediction, the CPMV offsetsare applied to the CPMVs of the first candidate. In Bi-prediction withList 0 and List 1 on the same direction, the CPMV offsets are applied tothe first candidate as follows:MV _(new(L0),i) =MV _(old(L0)) +MV _(offset(i))  Eq. (8)MV _(new(L1),i) =MV _(old(L1)) +MV _(offset(i))  Eq. (9)

In Bi-prediction with List 0 and List 1 on the opposite direction, theCPMV offsets are applied to the first candidate as follows:MV _(new(L0),i) =MV _(old(L0)) +MV _(offset(i))  Eq. (10)MV _(new(L1),i) =MV _(old(L1)) −MV _(offset(i))  Eq. (11)

Various offset directions with various offset magnitudes can be used togenerate new Affine merge candidates. Two implementations have beentested:

(1) 16 new Affine merge candidates with 8 different offset directionswith 2 different offset magnitudes are generated as shown in thefollowing offsets set:

Offset set={(4, 0), (0, 4), (−4, 0), (0, −4), (−4, −4), (4, −4), (4, 4),(−4, 4), (8, 0), (0, 8), (−8, 0), (0, −8), (−8, −8), (8, −8), (8, 8),(−8, 8)}.

The Affine merge list is increased to 20 for this design. The number ofpotential Affine merge candidates is 31 in total.

(2) 4 new Affine merge candidates with 4 different offset directionswith 1 offset magnitude are generated as shown in the following offsetsset:

Offset set={(4, 0), (0, 4), (−4, 0), (0, −4)}.

The Affine merge list is kept to 5 as VTM2.0.1 does. Four temporalconstructed Affine merge candidates are removed to keep the number ofpotential Affine merge candidates unchanged, e.g., 15 in total. Supposethe coordinates of CPMV1, CPMV2, CPMV3 and CPMV4 are (0, 0), (W, 0), (H,0) and (W, H). Note that CPMV4 is derived from the temporal MV as shownin FIG. 6. The removed candidates are the following fourtemporal-related constructed Affine merge candidates: {CP2, CP3, CP4},{CP1, CP4}, {CP2, CP4}, {CP3, CP4}.

2.7 Bandwidth Problem of Affine Motion Compensation

Since the current block is divided into 4×4 sub-blocks for lumacomponent and 2×2 sub-blocks for the two chroma components to do themotion compensation, the total bandwidth requirement is much higher thannon sub-block inter-prediction. To address the bandwidth problem,several approaches are proposed.

2.7.1 Example 1

4×4 block is used as the sub-block size for a uni-directional affinecoded CU while 8×4/4×8 block is used as the sub-block size for abi-directional affine coded CU.

2.7.2 Example 2

For affine mode, sub-block motion vectors of an affine CU areconstrained to be within a pre-defined motion vector field. Assume thatthe motion vectors of 1^(st) (top left) sub-block is (v_(0x),v_(0y)) andthe second sub-block is (v_(ix), v_(iy)), values of v_(ix) and v_(iy)exhibit the following constraints:v _(ix)∈[v _(0x) −H,v _(0x) +H]  Eq. (12)v _(iy)∈[v _(0y) −V,v _(0y) +V]  Eq. (13)

If the motion vector of any sub-block exceeds the pre-defined motionvector field, the motion vector is clipped. An illustration of the ideaof constrained sub-block motion vector is given in FIG. 6.

Assume memory is retrieved per CU instead of per sub-block, values H andV are chosen so that worst case memory bandwidth of affine CU will notexceed that of normal inter MC of a 8×8 bi-prediction block. Note thatvalues of H and V are adaptive to CU size and uni-prediction orbi-prediction.

2.7.3 Example 3

To reduce the memory bandwidth requirement in affine prediction, each8×8 block within the block is regarded as the basic unit. The MVs of allfour 4×4 sub-blocks inside the 8×8 block are constrained such that themax difference between integer parts of the four 4×4 sub-block MVs is nomore than 1 pixel. So that the bandwidth is (8+7+1)*(8+7+1)/(8*8)=4sample/pixel.

In some cases, after the MVs of all sub-blocks inside the current blockare calculated with affine model, the MV of the sub-blocks containingthe control points are firstly replaced with the corresponding controlpoint MV. This means that, the MV of the top-left, top-right andbottom-left sub-blocks are replaced by the top-left, top-right andbottom-left control points MV, respectively. Then, for each 8×8 blockwithin the current block, the MVs of all four 4×4 sub-blocks are clippedto guarantee the max difference between integer parts of the four MVs nomore than 1 pixel. Here it should be noted that the sub-blockscontaining the control points (top-left, top-right and bottom-leftsub-blocks) use the corresponding control point MV to involve in the MVclipping process. During the clipping process, the MV of the top-rightcontrol point is kept un-changed.

The clipping process applied to each 8×8 block is described as follows:

1. the minimal and maximal values for the MV components, MV minx,MVminy, MVmaxx, MVmaxy are firstly determined for each 8×8 block asfollows:

a) Get the minimal MV component among the four 4×4 sub-block MVsMVminx=min(MVx0,MVx1,MVx2,MVx3)MVminy=min(MVy0,MVy1,MVy2,MVy3)

b) Use the integer part of MVminx and MVminy as the minimal MV componentMVminx=MV minx>>MV_precision<<MV_precisionMVminy=MVminy>>MV_precision<<MV_precision

c) The maximal MV component is calculated as follows:MVmaxx=MV minx+(2<<MV_precision)−1MVmaxy=MVminy+(2<<MV_precision)−1

d) if the top-right control point is in current 8×8 blockif (MV1x>MVmaxx)MVminx=(MV1x>>MV_precision<<MV_precision)−(1<<MV_precision)MVmaxx=MVminx+(2<<MV_precision)−1if (MV1y>MVmaxy)MVminy=(MV1y>>MV_precision<<MV_precision)−(1<<MV_precision)MVmaxy=MVminy+(2<<MV_precision)−1

2. The MV components of each 4×4 block inside this 8×8 block are clippedas follows:MVxi=max(MV minx,min(MVmaxx,MVxi))MVyi=max(MVminy,min(MVmaxy,MVyi))

where (MVxi, MVyi) is the MV of ith sub-block within one 8×8 block,where i is 0, 1, 2, 3; (MV1x, MV1y) is the MV of the top-right controlpoint; MV_precision is equal to 4 corresponding to 1/16 motion vectorfraction accuracy. Since the difference between integer parts of MV minxand MVmaxx (MVminy and MVmaxy) is 1 pixel, the max difference betweeninteger parts of the four 4×4 sub-block MVs is no more than 1 pixel.

A similar method may also be used to handle the planar mode in someembodiments.

2.7.4 Example 4

In some embodiments, the restrictions to the affine mode for theworst-case bandwidth reduction. To ensure that the worst-case bandwidthof the affine block is not worse than an INTER_4×8/INTER_8×4 block oreven an INTER_9×9 block, the motion vector differences between affinecontrol points are used to decide whether the subblock size of theaffine block is 4×4 or 8×8.

General Affine Restriction for Worst-Case Bandwidth Reduction

The memory bandwidth reduction for the affine mode is controlled byrestricting the motion vector difference between the affine controlpoints (also named as the control points difference). In general, if thecontrol points differences satisfy the restriction below, the affinemotion is using 4×4 subblocks (namely 4×4 affine mode). Otherwise, it isusing 8×8 subblocks (8×8 affine mode). The restrictions for the6-parameters and 4-parameters model are given as follows.

To derive the constraints for different block sizes (w×h), the motionvector differences of the control points are normalized as:

$\begin{matrix}{{{{Norm}\left( {v_{1x} - v_{0x}} \right)} = {\left( {v_{1x} - v_{0x}} \right)*\frac{128}{w}}}{{{Norm}\left( {v_{1y} - v_{0y}} \right)} = {\left( {v_{1y} - v_{0y}} \right)*\frac{128}{w}}}{{{Norm}\left( {v_{2x} - v_{0x}} \right)} = {\left( {v_{2x} - v_{0x}} \right)*\frac{128}{h}}}{{{Norm}\left( {v_{2x} - v_{0x}} \right)} = {\left( {v_{2x} - v_{0x}} \right)*128\text{/}h}}} & {{Eq}.\mspace{14mu}(14)}\end{matrix}$

In the 4-parameters affine model, (v_(2x)−v_(0x)) and (v_(2y)−v_(0y))are set as the follows:(v _(2x) −v _(0x))=−(v _(1y) −v _(0y))(v _(2y) −v _(0y))=−(v _(1x) −v _(0x))  Eq. (15)

Hence, the Norms of (v_(2x)−v_(0x)) and (v_(2y)−v_(0y)) are given as:Norm(v _(2x) −v _(0x))=−Norm(v _(1y) −v _(0y))Norm(v _(2y) −v _(0y))=Norm(v _(1x) −v _(0x))  Eq. (16)

The restriction to ensure the worst-case bandwidth is achieve anINTER_4×8 or INTER_8×4:|Norm(v _(1x) −v _(0x))+Norm(v _(2x) −v _(0x))+128|+|Norm(v _(1y) −v _(0y))+Norm(v _(2y) −v _(0y))+128|+|Norm(v _(1x) −v _(0x))−Norm(v _(2x) −v _(0x))|+|Norm(v _(1y) −v _(0y))−Norm(v _(2y) −v _(0y))|<128*3.25  Eq. (17)

where the left-hand side of Eq. (18) represents the shrink or span levelof the sub affine blocks while (3.25) indicates 3.25 pixels shift.

The restriction to ensure the worst-case bandwidth is achieve anINTER_9×9(4*Norm(v _(1x) −v _(0x))>−4*pel&&+4*Norm(v _(1x) −v _(0x))<pel)&&(4*Norm(v _(1y) −v _(0y))>−pel&& 4*Norm(v _(1y) −v _(0y))<pel)&&(4*Norm(v _(2x) −v _(0x))>−pel&& 4*Norm(v _(2x) −v _(0x))<pel)&&(4*Norm(v _(2y) −v _(0y))>−4*pel&& 4*Norm(v _(2y) −v _(0y))<pel)&&((4*Norm(v _(1x) −v _(0x))+4*Norm(v _(2x) −v _(0x))>−4*pel)&&(4*Norm(v _(1x) −v _(0x))+4*Norm(v _(2x) −v _(0x))<pel))&&((4*Norm(v _(1y) −v _(0y))+4*Norm(v _(2y) −v _(0y))>−4*pel)&&(4*Norm(v _(1y) −v _(0y))+4*Norm(v _(2y) −v _(0y))<pel))  Eq. (18)

where pel=128*16 (128 and 16 indicate the normalization factor andmotion vector precision, respectively).

2.8 Generalized Bi-Prediction Improvement

Some embodiments improved the gain-complexity trade-off for GBi and wasadopted into BMS2.1. GBi is also referred to Bi-prediction with CU-levelweight (BCW). The BMS2.1 GBi applies unequal weights to predictors fromL0 and L1 in bi-prediction mode. In inter prediction mode, multipleweight pairs including the equal weight pair (½, ½) are evaluated basedon rate-distortion optimization (RDO), and the GBi index of the selectedweight pair is signaled to the decoder. In merge mode, the GBi index isinherited from a neighboring CU. In BMS2.1 GBi, the predictor generationin bi-prediction mode is shown in Eq. (19).P _(GBi)=(w ₀ *P _(L0) +w ₁ *P_(L1)+RoundingOffset_(GBi))>>shiftNum_(GBi),  Eq. (19)

where P_(GBi) is the final predictor of GBi. w₀ and w₁ are the selectedGBi weight pair and applied to the predictors of list 0 (L0) and list 1(L1), respectively. RoundingOffset_(GBi) and shiftNum_(GBi) are used tonormalize the final predictor in GBi. The supported w₁ weight set is{−¼, ⅜, ½, ⅝, 5/4}, in which the five weights correspond to one equalweight pair and four unequal weight pairs. The blending gain, e.g., sumof w₁ and w₀, is fixed to 1.0. Therefore, the corresponding w₀ weightset is {5/4, ⅝, ½, ⅜, −¼}. The weight pair selection is at CU-level.

For non-low delay pictures, the weight set size is reduced from five tothree, where the w₁ weight set is {⅜, ½, ⅝} and the w₀ weight set is {⅝,½, ⅜}. The weight set size reduction for non-low delay pictures isapplied to the BMS2.1 GBi and all the GBi tests in this contribution.

In some embodiments, the following modifications are applied on top ofthe existing GBi design in the BMS2.1 to further improve the GBiperformance.

2.8.1 GBi Encoder Bug Fix

To reduce the GBi encoding time, in current encoder design, the encoderwill store uni-prediction motion vectors estimated from GBi weight equalto 4/8, and reuse them for uni-prediction search of other GBi weights.This fast encoding method is applied to both translation motion modeland affine motion model. In VTM2.0, 6-parameter affine model was adoptedtogether with 4-parameter affine model. The BMS2.1 encoder does notdifferentiate 4-parameter affine model and 6-parameter affine model whenit stores the uni-prediction affine MVs when GBi weight is equal to 4/8.Consequently, 4-parameter affine MVs may be overwritten by 6-parameteraffine MVs after the encoding with GBi weight 4/8. The stored6-parameter affine MVs may be used for 4-parameter affine ME for otherGBi weights, or the stored 4-parameter affine MVs may be used for6-parameter affine ME. The proposed GBi encoder bug fix is to separatethe 4-parameter and 6-parameter affine MVs storage. The encoder storesthose affine MVs based on affine model type when GBi weight is equal to4/8, and reuse the corresponding affine MVs based on the affine modeltype for other GBi weights.

2.8.2 CU Size Constraint for GBi

In this method, GBi is disabled for small CUs. In inter prediction mode,if bi-prediction is used and the CU area is smaller than 128 lumasamples, GBi is disabled without any signaling.

2.8.3 Merge Mode with GBi

With Merge mode, GBi index is not signaled. Instead it is inherited fromthe neighboring block it is merged to. When TMVP candidate is selected,GBi is turned off in this block.

2.8.4 Affine Prediction with GBi

When the current block is coded with affine prediction, GBi can be used.For affine inter mode, GBi index is signaled. For Affine merge mode, GBiindex is inherited from the neighboring block it is merged to. If aconstructed affine model is selected, GBi is turned off in this block.

2.9 Example Inter-Intra Prediction Mode (IIP)

With inter-intra prediction mode which is also referred to combinedinter and intra prediction (CIIP), multi-hypothesis prediction combinesone intra prediction and one merge indexed prediction. Such a block istreated as a special inter-coded block. In a merge CU, one flag issignaled for merge mode to select an intra mode from an intra candidatelist when the flag is true. For luma component, the intra candidate listis derived from 4 intra prediction modes including DC, planar,horizontal, and vertical modes, and the size of the intra candidate listcan be 3 or 4 depending on the block shape. When the CU width is largerthan the double of CU height, horizontal mode is exclusive of the intramode list and when the CU height is larger than the double of CU width,vertical mode is removed from the intra mode list. One intra predictionmode selected by the intra mode index and one merge indexed predictionselected by the merge index are combined using weighted average. Forchroma component, DM is always applied without extra signaling.

The weights for combining predictions are described as follow. When DCor planar mode is selected or the CB width or height is smaller than 4,equal weights are applied. For those CBs with CB width and height largerthan or equal to 4, when horizontal/vertical mode is selected, one CB isfirst vertically/horizontally split into four equal-area regions. Eachweight set, denoted as (w_intra_(i), w_inter_(i)), where i is from 1 to4 and (w_intra₁, w_inter₁)=(6, 2), (w_intra₂, w_inter₂)=(5, 3),(w_intra₃, w_inter₃)=(3, 5), and (w_intra₄, w_inter₄)=(2, 6), will beapplied to a corresponding region. (w_intra₁, w_inter₁) is for theregion closest to the reference samples and (w_intra₄, w_inter₄) is forthe region farthest away from the reference samples. Then, the combinedprediction can be calculated by summing up the two weighted predictionsand right-shifting 3 bits. Moreover, the intra prediction mode for theintra hypothesis of predictors can be saved for reference of thefollowing neighboring CUs.

Suppose intra and inter prediction values are PIntra and Pinter, and theweighting factor are w_intra and w_inter respectively. The predictionvalue at position (x, y) is calculated as (PIntra(x, y)*w_intra(x,y)+PInter(x, y)*w_inter(x, y))>>N, wherein w_intra(x, y)+w_iner(x,y)=2{circumflex over ( )}N.

Signaling of Intra Prediction Modes in IIP-Coded Blocks

When inter-intra mode is used, one of the four allowed intra-predictionmodes, DC, Planar, Horizontal and Vertical is selected and signaled.Three Most Probable Modes (MPMs) are constructed from the left and aboveneighboring blocks. The intra-prediction mode of an intra-codedneighboring block or an IIP-coded neighboring block is treated as oneMPM. If the intra-prediction mode is not one of the four allowedintra-prediction modes, it will be rounded to vertical mode orhorizontal mode depending on the angular difference. The neighboringblock must be in the same CTU line as the current block.

Suppose the width and height of the current block is W and H. If W>2*Hor H>2*W, then only one of the three MPMs can be used in the inter-intramode. Otherwise, all the four valid intra-prediction modes can be usedin the inter-intra mode.

It should be noted that the intra-prediction mode in inter-intra modecannot be used to predict intra-prediction mode in a normal intra-codedblock.

Inter-intra prediction can only be used when W*H>=64.

2.10 Example Triangular Prediction Mode

The concept of the triangular prediction mode (TPM) is to introduce anew triangular partition for motion compensated prediction. As shown inFIG. 7A-7B, it splits a CU into two triangular prediction units, ineither diagonal or inverse diagonal direction. Each triangularprediction unit in the CU is inter-predicted using its ownuni-prediction motion vector and reference frame index which are derivedfrom a uni-prediction candidate list. An adaptive weighting process isperformed to the diagonal edge after predicting the triangularprediction units. Then, the transform and quantization process areapplied to the whole CU. It is noted that this mode is only applied toskip and merge modes.

2.10.1 Uni-Prediction Candidate List for TPM

The uni-prediction candidate list consists of five uni-prediction motionvector candidates. It is derived from seven neighboring blocks includingfive spatial neighboring blocks (1 to 5) and two temporal co-locatedblocks (6 to 7), as shown in FIG. 8. The motion vectors of the sevenneighboring blocks are collected and put into the uni-predictioncandidate list according in the order of uni-prediction motion vectors,L0 motion vector of bi-prediction motion vectors, L1 motion vector ofbi-prediction motion vectors, and averaged motion vector of the L0 andL1 motion vectors of bi-prediction motion vectors. If the number ofcandidates is less than five, zero motion vector is added to the list.Motion candidates added in this list are called TPM motion candidates.

More specifically, the following steps are involved:

1) Obtain motion candidates from A₁, B₁, B₀, A₀, B₂, Col and Col2(corresponding to block 1-7 in FIG. 8) without any pruning operations.

2) Set variable numCurrMergeCand=0.

3) For each motion candidates derived from A₁, B₁, B₀, A₀, B₂, Col andCol2 and numCurrMergeCand is less than 5, if the motion candidate isuni-prediction (either from List 0 or List 1), it is added to the mergelist with numCurrMergeCand increased by 1. Such added motion candidatesis named ‘originally uni-predicted candidate’. Full pruning is applied.

4) For each motion candidates derived from A₁, B₁, B₀, A₀, B₂, Col andCol2 and numCurrMergeCand is less than 5, if the motion candidate isbi-prediction, the motion information from List 0 is added to the mergelist (that is, modified to be uni-prediction from List 0) andnumCurrMergeCand increased by 1. Such added motion candidates are named‘Truncated List0-predicted candidate’. Full pruning is applied.

5) For each motion candidates derived from A₁, B₁, B₀, A₀, B₂, Col andCol2 and numCurrMergeCand is less than 5, if the motion candidate isbi-prediction, the motion information from List 1 is added to the mergelist (that is, modified to be uni-prediction from List 1) andnumCurrMergeCand increased by 1. Such added motion candidates are named‘Truncated List1-predicted candidate’. Full pruning is applied.

6) For each motion candidates derived from A₁, B₁, B₀, A₀, B₂, Col andCol2 and numCurrMergeCand is less than 5, if the motion candidate isbi-prediction,

-   -   If List 0 reference picture's slice Quantization Parameter (QP)        is smaller than List 1 reference picture's slice QP, the motion        information of List 1 is firstly scaled to List 0 reference        picture, and the average of the two MVs (one is from original        List 0, and the other is the scaled MV from List 1) is added to        the merge list, that is averaged uni-prediction from List 0        motion candidate and numCurrMergeCand increased by 1.    -   Otherwise, the motion information of List 0 is firstly scaled to        List 1 reference picture, and the average of the two MVs (one is        from original List 1, and the other is the scaled MV from        List 0) is added to the merge list, that is averaged        uni-prediction from List 1 motion candidate and numCurrMergeCand        increased by 1.

Full pruning is applied.

7) If numCurrMergeCand is less than 5, zero motion vector candidates areadded.

2.11 Decoder-Side Motion Vector Refinement (DMVR) in VVC

For DMVR in VVC, MVD mirroring between list 0 and list 1 is assumed asshown in FIG. 13, and bilateral matching is performed to refine the MVs,e.g., to find the best MVD among several MVD candidates. Denote the MVsfor two reference picture lists by MVL0(L0X, L0Y), and MVL1(L1X, L1Y).The MVD denoted by (MvdX, MvdY) for list 0 that could minimize the costfunction (e.g., SAD) is defined as the best MVD. For the SAD function,it is defined as the SAD between the reference block of list 0 derivedwith a motion vector (L0X+MvdX, L0Y+MvdY) in the list 0 referencepicture and the reference block of list 1 derived with a motion vector(L1X−MvdX, L1Y−MvdY) in the list 1 reference picture.

The motion vector refinement process may iterate twice. In eachiteration, at most 6 MVDs (with integer-pel precision) may be checked intwo steps, as shown in FIG. 14. In the first step, MVD (0, 0), (−1, 0),(1, 0), (0, −1), (0, 1) are checked. In the second step, one of the MVD(−1, −1), (−1, 1), (1, −1) or (1, 1) may be selected and furtherchecked. Suppose function Sad(x, y) returns SAD value of the MVD (x, y).The MVD, denoted by (MvdX, MvdY), checked in the second step is decidedas follows:MvdX=−1;MvdY=−1;If (Sad(1,0)<Sad(−1,0))MvdX=1;If (Sad(0,1)<Sad(0,−1))MvdY=1;

In the first iteration, the starting point is the signaled MV, and inthe second iteration, the starting point is the signaled MV plus theselected best MVD in the first iteration. DMVR applies only when onereference picture is a preceding picture and the other reference pictureis a following picture, and the two reference pictures are with samepicture order count distance from the current picture.

To further simplify the process of DMVR, the following main features canbe implemented in some embodiments:

1. Early termination when (0,0) position SAD between list0 and list1 issmaller than a threshold.

2. Early termination when SAD between list0 and list1 is zero for someposition.

3. Block sizes for DMVR: W*H>=64 && H>=8, wherein W and H are the widthand height of the block.

4. Split the CU into multiple of 16×16 sub-blocks for DMVR of CUsize>16*16. If only width or height of the CU is larger than 16, it isonly split in vertical or horizontal direction.

5. Reference block size (W+7)*(H+7) (for luma).

6. 25 points SAD-based integer-pel search (e.g. (+−) 2 refinement searchrange, single stage)

7. Bilinear-interpolation based DMVR.

8. “Parametric error surface equation” based sub-pel refinement. Thisprocedure is performed only when the minimum SAD cost is not equal tozero and the best MVD is (0, 0) in the last MV refinement iteration.

9. Luma/chroma MC w/reference block padding (if needed).

10. Refined MVs used for MC and TMVPs only.

2.11.1 Usage of DMVR

When the following conditions are all true, DMVR may be enabled:

-   -   DMVR enabling flag in the SPS (e.g., sps_dmvr_enabled_flag) is        equal to 1.    -   TPM flag, inter-affine flag and subblock merge flag (either        ATMVP or affine merge), MMVD flag are all equal to 0.    -   Merge flag is equal to 1.    -   Current block is bi-predicted, and Picture Order Count (POC)        distance between current picture and reference picture in list 1        is equal to the POC distance between reference picture in list 0        and current picture.    -   The current CU height is greater than or equal to 8.    -   Number of luma samples (CU width*height) is greater than or        equal to 64.

2.11.2 “Parametric Error Surface Equation” Based Sub-Pel Refinement

The method is summarized below:

1. The parametric error surface fit is computed only if the centerposition is the best cost position in a given iteration.

2. The center position cost and the costs at (−1,0), (0,−1), (1,0) and(0,1) positions from the center are used to fit a 2-D parabolic errorsurface equation of the formE(x,y)=A(x−x ₀)² +B(y−y ₀)² +C

where (x₀,y₀) corresponds to the position with the least cost and Ccorresponds to the minimum cost value. By solving the 5 equations in 5unknowns, (x₀, y₀) is computed as:x ₀=(E(−1,0)−E(1,0))/(2(E(−1,0)+E(1,0)−2E(0,0)))y ₀=(E(0,−1)−E(0,1))/(2((E(0,−1)+E(0,1)−2E(0,0))

(x₀,y₀) can be computed to any required sub-pixel precision by adjustingthe precision at which the division is performed (e.g. how many bits ofquotient are computed). For 1/16^(th)-pel accuracy, just 4-bits in theabsolute value of the quotient needs to be computed, which lends itselfto a fast shifted subtraction based implementation of the 2 divisionsrequired per CU.

3. The computed (x₀,y₀) are added to the integer distance refinement MVto get the sub-pixel accurate refinement delta MV.

2.11.3 Required reference samples in DMVR

For a block with size W*H, suppose the maximum allowable MVD value is+/−offset (for example 2 in VVC), and the filter size is filteSize (forexample, 8 for luma and 4 for chroma in VVC), then(W+2*offSet+filterSize−1)*(H+2*offSet+filterSize−1) reference samplesare required. To reduce the memory bandwidth, only the center(W+filterSize−1)*(H+filterSize−1) reference samples are fetched, and theother pixels are generated by repeating the boundary of the fetchedsamples. Example for 8*8 block is shown in FIG. 15, 15*15 referencesamples are fetched, and the boundary of the fetched samples arerepeated to generate a 17*17 region.

During the motion vector refinement, bilinear motion compensation isperformed using these reference samples. Meanwhile, the final motioncompensation is also performed using these reference samples.

2.12 Bandwidth Calculation for Different Block Sizes

Based on the current 8-tap luma interpolation filter and 4-tap chromainterpolation filter, the memory bandwidth for each block unit (4:2:0color format, one M×N luma block with two M/2×N/2 chroma blocks) istabulated in Table 1 below.

TABLE 1 Example memory bandwidth Block Size M × N Samples Required/pixelUni Bi 4*4 (11*11 + 2*5*5)/(4*4) 10.688 21.375 4*8 (11*15 + 2*5*7)/(4*8)7.344 14.688 4*16 (11*23 + 2*5*11)/(4*16) 5.672 11.344 4*32 (11*39 +2*5*19)/(4*32) 4.836 9.672 4*64 (11*71 + 2*5*35)/(4*64) 4.418 8.8364*128 (11*135 + 2*5*67)/(4*128) 4.209 8.418 8*8 (15*15 + 2*7*7)/(8*8)5.047 10.094 8*16 (15*23 + 2*7*11)/(8*16) 3.898 7.797 8*32 (15*39 +2*7*19)/(8*32) 3.324 6.648 8*64 (15*71 + 2*7*35)/(8*64) 3.037 6.0748*128 (15*135 + 2*7*67)/(8*128) 2.894 5.787

Similarly, based on the current 8-tap luma interpolation filter and4-tap chroma interpolation filter, the memory bandwidth for each M×Nluma block unit is tabulated in Table 2 below.

TABLE 2 Example memory bandwidth Block Size M × N Samples Required/pixelUni Bi 4*4 (11*11)/(4*4) 7.563 15.125 4*8 (11*15)/(4*8) 5.156 10.3134*16 (11*23)/(4*16) 3.953 7.906 4*32 (11*39)/(4*32) 3.352 6.703 4*64(11*71)/(4*64) 3.051 6.102 4*128 (11*135)/(4*128) 2.900 5.801 8*8(15*15)/(8*8) 3.516 7.031 8*16 (15*23)/(8*16) 2.695 5.391 8*32(15*39)/(8*32) 2.285 4.570 8*64 (15*71)/(8*64) 2.080 4.160 8*128(15*135)/(8*128) 1.978 3.955

Therefore, regardless the color format, the bandwidth requirement foreach block size in descending order is:

4*4 Bi>4*8 Bi>4*16 Bi>4*4 Uni>8*8 Bi>4*32 Bi>4*64Bi>4*128 Bi>8*16 Bi>4*8Uni>8*32 Bi> . . . .

2.12 Motion Vector Precision Issues in VTM-3.0

In VTM-3.0, the MV precision is 1/16 luma pixel in storage. When MV issignaling, the finest precision is ¼ luma pixel.

3. Examples of Problems Solved by Disclosed Embodiments

1. The bandwidth control methods towards affine prediction are not clearenough and should be more flexible.

2. It is noted that in HEVC design, the worst case for memory bandwidthrequirement is 8×8 bi-prediction even a coding unit (CU) could be splitwith asymmetric prediction mode, such as one 16×16 split to two PUs withsize equal to 4×16 and 12×16. In VVC, due to the new QTBT partitionstructure, one CU could be set to 4×16 and bi-prediction could beenabled. bi-predicted 4×16 CU requires even higher memory bandwidthcompared to bi-predicted 8×8 CU. How to deal with block sizes (such as4×16 or 16×4) requiring higher bandwidth is unknown.

3. New coding tools, such as GBi, introduce more line buffer issues

4. Inter-intra mode requires more memory and logic to signal theintra-prediction mode used in an inter-coded block.

5. The 1/16 luma pixel MV precision requires a higher memory storage.

6. To interpolate four 4×4 blocks within one 8×8 block, it needs tofetch (8+7+1)*(8+7+1) reference pixels and requires around 14% morepixels when compared with non-affine/non-planar mode 8×8 block.

7. The averaging operation in hybrid intra and inter prediction shall bealigned with other coding tools, e.g., weighted prediction, localillumination compensation, OBMC and triangular prediction, wherein anoffset is added before the shift.

4. Examples of Embodiments

The techniques disclosed herein can reduce the bandwidth and linebuffers required in affine prediction and other new coding tools.

The description below should be considered as examples to explaingeneral concepts and should not be interpreted in a narrow way.Furthermore, the embodiments can be combined in any manner.

In the discussions below, the width and height of the affine codedcurrent CU are w and h, respectively. It is assumed that theinterpolation filter tap (in motion compensation) is N (for example, 8,6, 4, or 2), and the current block size is W×H.

Bandwidth Control for Affine Prediction

Example 1: Suppose the motion vector of a sub-block SB in an affinecoded block is MV_(SB) (denoted as (MVx, MVy)), MV_(SB) can be within acertain range relative to a representative motion vector MV′(MV′x,MV′y).

In some embodiments, MVx>=MV′x-DH0 and MVx<=MV′x+DH1 and MVy>=MV′y-DV0and MVy<=MV′y+DV1, where MV′=(MV′x, MV′y). In some embodiments, DH0 maybe equal to DH1 or not; DV0 may be equal to DV1 or not. In someembodiments, DH0 may be equal to DV0 or not; DH1 may be equal to DV1 ornot.

In some embodiments, DH0 may be not equal to DH1; DV0 may be not equalto DV1. In some embodiments, DH0, DH1, DV0 and DV1 may be signaled fromencoder to decoder, such as in VPS/SPS/PPS/Slice header/tile groupheader/tile/CTU/CU/PU. In some embodiments, DH0, DH1, DV0 and DV1 may bespecified differently for different standard profiles/levels/tiers. Insome embodiments, DH0, DH1, DV0 and DV1 may depend on the width andheight of the current block. In some embodiments, DH0, DH1, DV0 and DV1may depend on whether the current block is uni-prediction orbi-prediction. In some embodiments, DH0, DH1, DV0 and DV1 may depend onthe position of the sub-block SB. In some embodiments, DH0, DH1, DV0 andDV1 may depend on how to get MV′.

In some embodiments, MV′ can be one CPMV such as MV0, MV1 or MV2.

In some embodiments, MV′ can be the MV used in MC for one of the cornersub-block, such as MV0′, MV1′ or MV2′ in FIG. 3.

In some embodiments, MV′ can be the MV derived for any position insideor outside the current block with the affine model of the current block.For example, it may be derived for center position of the current block(e.g., x=w/2 and y=h/2).

In some embodiments, MV′ can be the MV used in MC for any sub-block ofthe current block, such as one of the center sub-blocks (C0, C1, C2 orC3 shown in FIG. 3).

In some embodiments, If MV_(SB) does not satisfy the constrain, MV_(SB)should be clipped to the valid range. In some embodiments, the clippedMV_(SB) is stored into the MV buffer, which will be used to predict theMVs of following coded blocks. In some embodiments, the MV_(SB) beforebeing clipped is stored into the MV buffer.

In some embodiments, if MV_(SB) does not satisfy the constrain, thebit-stream is considered as not conforming to the standard (invalid). Inone example, it can be specified in a standard that MV_(SB) must orshould satisfy the constrain. This constrains should be followed by anyconforming encoder, otherwise, the encoder is regarded as not conformingto the standard.

In some embodiments, MV_(SB) and MV′ may be represented with thesignaling MV precision (such as quarter-pixel precision). In someembodiments, MV_(SB) and MV′ may be represented with the storage MVprecision (such as 1/16 precision). In some embodiments, MV_(SB) and MV′may be rounded to a precision (such as the integer precision) differentfrom the signaling or storage precision.

Example 2: For an affine coded block, each M×N (such as 8×4,4×8 or 8×8)block within the block is regarded as the basic unit. The MVs of all 4×4sub-blocks inside the M×N are constrained such that the max differencebetween integer parts of the four 4×4 sub-block MVs is no more than Kpixel.

In some embodiments, whether to and how to apply this constrain dependson whether the current block applies bi-prediction or uni-prediction.For example, the constrain is applied only for bi-prediction, not foruni-prediction. As another example, M, N and K are different forbi-prediction and uni-prediction.

In some embodiments, M, N and K may depend on the width and height ofthe current block.

In some embodiments, whether to apply the constrain may be signaled fromencoder to decoder, such as in VPS/SPS/PPS/Slice header/tile groupheader/tile/CTU/CU/PU. For example, an on/off flag is signaled toindicate whether to apply the constrain. As another example, M, N and Kare signaled.

In some embodiments, M, N and K may be specified differently fordifferent standard profiles/levels/tiers.

Example 3: The width and height of a sub-block may be calculateddifferently for different affine coded blocks.

In some embodiments, the calculation methods are different for an affinecoded block with uni-prediction and bi-prediction. In one example, thesub-block size is fixed (such as 4×4, 4×8 or 8×4) for a block withuni-prediction. In another example, the sub-block size is calculated forblocks with bi-prediction. In this case, sub-block size could bedifferent for two different bi-predicted affine blocks.

In some embodiments, for bi-predicted affine blocks, the width and/orheight of a sub-block from reference list 0 and the width and/or heightof a sub-block from reference list 1 may be different. In one example,suppose the width and height of a sub-block from reference list 0 arederived as Wsb0 and Hsb0, respectively; the width and height of asub-block from reference list 1 are derived as Wsb1 and Hsb1,respectively. Then the final width and height of sub-block for bothreference list 0 and reference list 1 are calculated as Max(Wsb0, Wsb1)and Max(Hsb0, HSb1), respectively.

In some embodiments, the calculated width and height of a sub-block areonly applied on the luma component. For chroma component, it is alwaysfixed, such as 4×4 chroma sub-block, which corresponds to an 8×8 lumablock with the 4:2:0 color format.

In some embodiments, MVx-MV′x and MVy−MV′y are calculated to decide thewidth and height of a sub-block. (MVx, MVy) and (MV′x, MV′y) are definedin Example 1.

In some embodiments, MVs involved in the calculation may be representedwith the signaling MV precision (such as quarter-pixel precision). Inone example, these MVs may be represented with the storage MV precision(such as 1/16 precision). As another example, these MVs may be roundedto a precision (such as the integer precision) different from thesignaling or storage precision.

In some embodiments, the thresholds used in the calculation to decidethe width and height of a sub-block may be signaled from encoder todecoder, such as in VPS/SPS/PPS/Slice header/tile groupheader/tile/CTU/CU/PU.

In some embodiments, the thresholds used in the calculation to decidethe width and height of a sub-block may be different for differentstandard profiles/levels/tiers.

Example 4: To interpolate W1×H1 sub-blocks within one W2×H2sub-block/block, a (W2+N−1−PW)*(H2+N−1−PH) block is first fetched andthen pixel padding method (e.g., the boundary pixel repeating method)described in Example [00353] is applied to generate a larger block,which is then used to interpolate the W1×H1 sub-blocks. For example,W2=H2=8, W1=H1=4 and PW=PH=0.

In some embodiments, integer part of MV of any W1×H1 sub-block may beused to fetch the entire W2×H2 sub-block/block, and different boundarypixel repeating method may be required accordingly. For example, if themaximum difference between integer parts of all W1×H1 sub-block MVs isno more than 1 pixel, integer part of MV of the top-left W1×H1 sub-blockis used to fetch the entire W2×H2 sub-block/block. The right and bottomboundary of the reference block are repeated once. As another example,if the maximum difference between integer parts of all W1×H1 sub-blockMVs is no more than 1 pixel, integer part of MV of the bottom-rightW1×H1 sub-block is used to fetch the entire W2×H2 sub-block/block. Theleft and top boundary of the reference block are repeated once.

In some embodiments, MV of any W1×H1 sub-block may be first modified andthen used to fetch the entire W2×H2 sub-block/block, and differentboundary pixel repeating method may be required accordingly. Forexample, if the maximum difference between integer parts of all W1×H1sub-block MVs is no more than 2 pixels, integer part of MV of thetop-left W1×H1 sub-block may be added by (1, 1) (here 1 means 1 integerpixel distance) and is then used to fetch the entire W2×H2sub-block/block. In this case, the left, right, top and bottom boundaryof the reference block are repeated once. As another example, if themaximum difference between integer parts of all W1×H1 sub-block MVs isno more than 2 pixels, integer part of MV of the bottom-right W1×H1sub-block may be added by (−1, −1) (here 1 means 1 integer pixeldistance) and is then used to fetch the entire W2×H2 sub-block/block. Inthis case, the left, right, top and bottom boundary of the referenceblock are repeated once.

Bandwidth Control for Specific Block Sizes

Example 5: Bi-prediction is not allowed if w and h of the current blocksatisfy one or more of the conditions as below.

A. w is equal to T1 and h is equal to T2, or h is equal to T1 and w isequal to T2.

In one example, T1=4 and T2=16.

B. w is equal to T1 and h is not greater than T2, or h is equal to T1and w is not greater than T2. In one example, T1=4 and T2=16.

C. w is not greater than T1 and h is not greater than T2, or h is notgreater than T1 and w is not greater than T2. In one example, T1=8 andT2=8. In another example, T1==8, T2==4. In still another example, T1==4and T2==4.

In some embodiments, bi-prediction may be disabled for 4×8 blocks. Insome embodiments, bi-prediction may be disabled for 8×4 blocks. In someembodiments, bi-prediction may be disabled for 4×16 blocks. In someembodiments, bi-prediction may be disabled for 16×4 blocks. In someembodiments, bi-prediction may be disabled for 4×8, 8×4 blocks. In someembodiments, bi-prediction may be disabled for 4×16, 16×4 blocks. Insome embodiments, bi-prediction may be disabled for 4×8, 16×4 blocks. Insome embodiments, bi-prediction may be disabled for 4×16, 8×4 blocks. Insome embodiments, bi-prediction may be disabled for 4×N blocks, forexample, N<=16. In some embodiments, bi-prediction may be disabled forN×4 blocks, for example, N<=16. In some embodiments, bi-prediction maybe disabled for 8×N blocks, for example, N<=16. In some embodiments,bi-prediction may be disabled for N×8 blocks, for example, N<=16. Insome embodiments, bi-prediction may be disabled for 4×8, 8×4, 4×16blocks. In some embodiments, bi-prediction may be disabled for 4×8, 8×4,16×4 blocks. In some embodiments, bi-prediction may be disabled for 8×4,4×16, 16×4 blocks. In some embodiments, bi-prediction may be disabledfor 4×8, 8×4, 4×16, 16×4 blocks.

In some embodiments, the block size disclosed in this document may referto one color component such as the luma component, and the decision onwhether bi-prediction is disabled can be applied to all colorcomponents. For example, if bi-prediction is disabled according to theblock size of the luma component for a block, bi-prediction will also bedisabled for corresponding blocks of other color components. In someembodiments, the block size disclosed in this document may refer to onecolor component such as the luma component, and the decision on whetherbi-prediction is disabled can only be applied to that color component.

In some embodiments, if bi-prediction is disabled for a block, and theselected merge candidate is bi-predicted, then only one MV fromreference list 0 or reference list 1 of the merge candidate is assignedto the block.

In some embodiments, Triangular Prediction Mode (TPM) is not allowed fora block if bi-prediction is disabled for the block.

In some embodiments, how to signal the prediction direction(uni-prediction from list 0/1, bi-prediction) may depend on the blockdimension. In one example, when 1) block width*block height<64 or 2)block width*block height=64 but width is unequal to height, theindication of uni-prediction from list 0/1 may be signaled. As anotherexample, when 1) block width*block height>64 or 2)n width*blockheight=64 and width is equal to height, the indication of uni-predictionfrom list 0/1 or bi-prediction may be signaled.

In some embodiments, both uni-prediction and bi-prediction may bedisabled for 4×4 blocks. In some embodiments, it may be disabled foraffine coded blocks. Alternatively, it may be disabled for non-affinecoded blocks. In some embodiments, the indication of quad-tree split foran 8×8 block, binary tree split for 8×4 or 4×8 block, triple tree splitfor an 4×16 or 16×4 block may be skipped. In some embodiments, a 4×4block must be coded as an intra-block. In some embodiments, the MV for a4×4 block must be in integer-precision. For example, the IMV flag for a4×4 block must be 1. As another example, the MV for a 4×4 block must berounded to integer-precision.

In some embodiments, bi-prediction is allowed. However, suppose theinterpolation filter tap is N, instead of fetching (W+N−1)*(H+N−1)reference pixels, only (W+N−1−PW)*(W+N−1−PH) reference pixels arefetched. Meanwhile, pixels at the reference block boundaries (top, left,bottom and right boundary) are repeated to generate a (W+N−1)*(H+N−1)block as shown in FIG. 9 which is used for the final interpolation. Insome embodiments, PH is zero, and only left or/and right boundaries arerepeated. In some embodiments, PW is zero, and only top or/and bottomboundaries are repeated. In some embodiments, both PW and PH are greaterthan zero, and first the left or/and the right boundaries are repeated,and then the top or/and bottom boundaries are repeated. In someembodiments, both PW and PH are greater than zero, and first the topor/and bottom boundaries are repeated, and then the left and rightboundaries are repeated. In some embodiments, the left boundary isrepeated by M1 times and the right boundary is repeated by PW−M1 times.In some embodiments, the top boundary is repeated by M2 times and thebottom boundary is repeated by PH−M2 times. In some embodiments, suchboundary pixels repeating method may be applied to some of or allreference blocks. In some embodiments, PW and PH may be different fordifferent color components such as Y, Cb and Cr.

FIG. 9 shows an example of repeat boundary pixels of the reference blockbefore the interpolation.

Example 6: In some embodiments, (W+N−1−PW)*(W+N−1−PH) reference pixels(instead of (W+N−1)*(H+N−1) reference pixels) may be fetched for motioncompensation of W×H block. The samples out of the range(W+N−1−PW)*(W+N−1−PH) but inside the range (W+N−1)*(H+N−1) are padded todo the interpolation process. In one padding method, pixels at thereference block boundaries (top, left, bottom and right boundary) arerepeated to generate a (W+N−1)*(H+N−1) block as shown in FIG. 11, whichis used for the final interpolation.

In some embodiments, PH is zero, and only left or/and right boundariesare repeated.

In some embodiments, PW is zero, and only top or/and bottom boundariesare repeated.

In some embodiments, both PW and PH are greater than zero, and first theleft or/and the right boundaries are repeated, and then the top or/andbottom boundaries are repeated.

In some embodiments, both PW and PH are greater than zero, and first thetop or/and bottom boundaries are repeated, and then the left and rightboundaries are repeated.

In some embodiments, the left boundary is repeated by M1 times and theright boundary is repeated by PW−M1 times.

In some embodiments, the top boundary is repeated by M2 times and thebottom boundary is repeated by PH−M2 times.

In some embodiments, such boundary pixels repeating method may beapplied to some of or all reference blocks.

In some embodiments, PW and PH may be different for different colorcomponents such as Y, Cb and Cr.

In some embodiments, PW and PH may be different for different block sizeor shape.

In some embodiments, PW and PH may be different for uni-prediction andbi-prediction.

In some embodiments, padding may be not performed in affine mode.

In some embodiments, the samples out of the range (W+N−1−PW)*(W+N−1−PH)but inside the range (W+N−1)*(H+N−1) are set to be a single value. Insome embodiments, the single value is 1<<(BD-1), where BD is thebit-depth the samples, such as 8 or 10. In some embodiments, the singlevalue is signalled from the encoder to the decoder in VPS/SPS/PPS/sliceheader/tile group header/tile/CTU row/CTU/CU/PU.

In some embodiments, the single value is derived from samples inside therange (W+N−1−PW)*(W+N−1−PH).

Example 7: Instead of fetching (W+filterSize−1)*(H+filterSize−1)reference samples in DMVR, (W+filterSize−1−PW)*(H+filterSize−1−PH)reference samples may be fetched, and all other required samples may begenerated by repeating the boundary of the fetched reference samples,wherein PW>=0 and PH>=0.

In some embodiments, method proposed in Example [00353] may be used topad the non-fetched samples.

In some embodiments, in the final motion compensation of DMVR, paddingmay be not performed again.

In some embodiments, whether to apply the above methods may depend onthe block dimension.

Example 8: The signaling method of inter_pred_idc may depend on whetherw and h satisfy the conditions in Example 5. One example is shown inTable 3 below:

TABLE 3 Name of inter_pred_idc !((w==T1 && h==T2) (w==T1 && h==T2)inter_pred_idc ∥(h==T1 && w==T2)) ∥(h==T1 && w==T2) 0 PRED_L0 PRED_L0 1PRED_L1 PRED_L1 2 PRED_BI n.a.

Another example is shown in Table 4 below:

TABLE 4 Name of inter_pred_idc !((w==T1 && h<=T2) (w==T1 && h<=T2)inter_pred_idc ∥(h==T1 && w<=T2)) ∥(h==T1 && w<=T2) 0 PRED_L0 PRED_L0 1PRED_L1 PRED_L1 2 PRED_BI n.a.

Yet another example is shown in Table 5 below:

TABLE 5 Name of inter_pred_idc !((w<=T1 && h<=T2) (w<=T1 && h<=T2)inter_pred_idc ∥(h<=T1 && w<=T2)) ∥(h<=T1 && w<=T2) 0 PRED_L0 PRED_L0 1PRED_L1 PRED_L1 2 PRED_BI n.a.

Example 9: The merge candidate list construction process may depend onwhether w and h satisfy the conditions in Example 4. The followingembodiments describe cases when w and h satisfy the conditions.

In some embodiments, if one merge candidate uses bi-prediction, thenonly the prediction from reference list 0 is retained, and the mergecandidate is treated as uni-prediction referring to reference list 0.

In some embodiments, if one merge candidate uses bi-prediction, thenonly the prediction from reference list 1 is retained, and the mergecandidate is treated as uni-prediction referring to reference list 1.

In some embodiments, if one merge candidate uses bi-prediction, then thecandidate is treated as unavailable. That is, such a merge candidate isremoved from the merge list.

In some embodiments, the merge candidate list construction process forTriangular Prediction Mode is used instead.

Example 10: The coding tree split process may depend on whether thewidth and height of a child CU after the split satisfies the conditionsin Example 5.

In some embodiments, if the width and height of a child CU after thesplit satisfies the conditions in Example 5, then the split is notallowed. In some embodiments, the signaling of coding tree split maydepend on whether one kind of split is allowed or not.

In one example, if one kind of split is not allowed, the codewordrepresenting the split is omitted.

Example 11: Signaling of skip flag or/and Intra Block Copy (IBC) flagmay depend on whether the width and/or height of the block satisfiescertain conditions (e.g., conditions mentioned in Example 5).

In some embodiments, the condition is that the luma block contains nomore than X samples. E.g. X=16;

In some embodiments, the condition is that the luma block contains Xsamples. E.g. X=16.

In some embodiments, the condition is that the luma block's width andheight are both equal to X. e.g. X=4;

In some embodiments, when the one or some of the above conditions aretrue, inter mode and/or IBC mode is disallowed for such a block.

In some embodiments, if inter mode is disallowed for a block, skip flagmay be not signaled for it. Alternatively, furthermore, the skip flagmay be inferred to be false.

In some embodiments, if inter mode and IBC mode are disallowed for ablock, skip flag may be not signaled for it and may be derived to befalse implicitly (e.g., the block is derived to be coded in non-skipmode).

In some embodiments, if inter mode is disallowed for a block but IBCmode is allowed for the block, skip flag may be still signaled. In someembodiments, IBC flag may be not signaled if the block is coded in skipmode, and the IBC flag is derived to be true implicitly (e.g., the blockis derived to be coded in IBC mode).

Example 12: Signaling of prediction mode may depend on whether the widthand/or height of the block satisfies certain conditions (e.g.,conditional mentioned in Example 5).

In some embodiments, the condition is that the luma block contains nomore than 1×6 samples, e.g. X=16.

In some embodiments, the condition is that the luma block contains Xsamples, e.g. X=16.

In some embodiments, the condition is that the luma block's width andheight are both equal to X, e.g. X=4.

In some embodiments, when one or some of the above conditions are true,inter mode and/or IBC mode is disallowed for such a block.

In some embodiments, signaling of indications of certain modes may beskipped.

In some embodiments, if inter mode and IBC mode are disallowed for ablock, signalling of indications of inter and IBC modes is skipped,remaining allowed modes may be still signaled, such as whether it isintra mode or palette mode.

In some embodiments, if inter mode and IBC mode are disallowed for ablock, prediction mode may be not signaled. Alternatively, furthermore,and the prediction mode may be derived to be intra mode implicitly.

In some embodiments, if inter mode is disallowed for a block, signallingof indications of inter modes is skipped, remaining allowed modes may bestill signaled, such as whether it is intra mode or IBC mode.Alternatively, remaining allowed modes may be still signaled, such aswhether it is intra mode or IBC mode or palette mode.

In some embodiments, if inter mode is disallowed for a block but IBCmode and intra mode are allowed for it, IBC flag may be signaled toindicate whether the block is coded in IBC mode or not. Alternatively,furthermore, prediction mode may be not signaled.

Example 13: Signaling of triangle mode may depend on whether the widthand/or height of the block satisfies certain conditions (e.g.,conditional mentioned in Example 5).

In some embodiments, the condition is that the luma block size is one ofsome specific sizes. For example, the specific sizes may include 4×16or/and 16×4.

In some embodiments, when the above condition is true, triangle mode maybe disallowed, and the flag indicating whether the current block iscoded in triangle mode may be not signaled and may be derived to befalse.

Example 14: Signaling of inter prediction direction may depend onwhether the width and/or height of the block satisfies certainconditions (e.g., conditional mentioned in Example 5).

In some embodiments, the condition is that the luma block size is one ofsome specific sizes. For example, the specific sizes may include 8×4or/and 4×8 or/and 4×16 or/and 16×4.

In some embodiments, when the above condition is true, the block may beonly uni-predicted, and the flag indicating whether the current block isbi-predicted may be not signaled and may be derived to be false.

Example 15: Signaling of SMVD (symmetric MVD) flag may depend on whetherthe width and/or height of the block satisfies certain conditions (e.g.,conditional mentioned in Example 5).

In some embodiments, the condition is that the luma block size is one ofsome specific sizes. In some embodiments, the condition is defined aswhether block size has no more than 32 samples. In some embodiments, thecondition is defined as whether block size is 4×8 or 8×4. In someembodiments, the condition is defined as whether block size is 4×4, 4×8or 8×4. In some embodiments, the specific sizes may include 8×4 or/and4×8 or/and 4×16 or/and 16×4.

In some embodiments, when certain conditions are true, the indication ofusage of SMVD (such as SMVD flag) may be not signaled and may be derivedto be false. For example, the block may be set to uni-predicted.

In some embodiments, when certain conditions are true, the indication ofusage of SMVD (such as SMVD flag) may be still signaled, however, onlylist 0 or list 1 motion information may be utilized in the motioncompensation process.

Example 16: Motion vectors (like motion vectors derived in regular mergemode, ATMVP mode, MMVD merge mode, MMVD skip mode etc.) or block vectorsused for IBC, may be modified depending on whether the width and/orheight of the block satisfies certain conditions.

In some embodiments, the condition is that the luma block size is one ofsome specific sizes. For example, the specific sizes may include 8×4or/and 4×8 or/and 4×16 or/and 16×4.

In some embodiments, when the above condition is true, motion vectors orblock vectors of the block may be changed to uni-directional motionvectors, if the derived motion information is bi-prediction (e.g.,inherited from a neighboring block with some offsets). Such a process iscalled converting process and the final uni-directional motion vector isnamed as ‘converted uni-directional’ motion vector. In some embodiments,motion information of reference picture list X (e.g., X is 0 or 1) maybe kept and the motion information and that of list Y (Y being 1−X) maybe discarded. In some embodiments, motion information of referencepicture list X (e.g., X is 0 or 1) and that of list Y (Y being 1−X) maybe jointly utilized to derive a new motion candidate point to list X. Inone example, the motion vector of the new motion candidate may be theaveraged motion vector of two reference picture lists. As anotherexample, motion information of list Y may be scaled to list X firstly.Then the motion vector of the new motion candidate may be the averagedmotion vector of two reference picture lists. In some embodiments,motion vectors in prediction direction X may be not used (e.g., motionvector in prediction direction X is changed to (0, 0), and referenceindex in prediction direction X is changed to −1), and predictiondirection may be changed to 1−X, X=0 or 1. In some embodiments, theconverted uni-directional motion vectors may be used to update the HMVPlookup table. In some embodiments, the derived bi-directional motioninformation, e.g., the bi-directional MVs before converted touni-directional MVs, may be used to update the HMVP lookup table. Insome embodiments, the converted uni-directional motion vectors may bestored and may be used for motion prediction of following coded blocks,TMVP, deblocking, etc. In some embodiments, the derived bi-directionalmotion information, e.g., the bi-directional MVs before converted touni-directional MVs, may be stored and may be used for motion predictionof following coded blocks, TMVP, deblocking, etc. In some embodiments,the converted uni-directional motion vectors may be used for motionrefinement. In some embodiments, the derived bi-directional motioninformation may be used for motion refinement and/or sample refinement,such as with the optical flow methods. In some embodiments, theprediction blocks generated according to the derived bi-directionalmotion information may be firstly refined, afterwards, only oneprediction block may be utilized to derive the final prediction and/orreconstruction block of one block.

In some embodiments, when certain conditions are true, (bi-predicted)motion vectors may be converted to uni-directional motion vectors beforebeing used as the base merge candidates in MMVD.

In some embodiments, when certain conditions are true, (bi-predicted)motion vectors may be converted to uni-directional motion vectors beforebeing inserted into the merge list.

In some embodiments, the converted uni-directional motion vectors may befrom reference list 0 only. In some embodiments, when the currentslice/tile group/picture is bi-predicted, the converted uni-directionalmotion vectors may be from reference list 0 or list 1. In someembodiments, when the current slice/tile group/picture is bi-predicted,the converted uni-directional motion vectors from reference list 0 andlist 1 may be interleaved in merge list or/and MMVD base merge candidatelist.

In some embodiments, how to convert motion information touni-directional motion vectors may depend on reference pictures. In someembodiments, if all reference pictures of one video data unit (such astile/tile group) are past pictures in the display order, list 1 motioninformation may be utilized. In some embodiments, if at least one ofreference pictures of one video data unit (such as tile/tile group) is apast picture, and at least one is a future picture, in the displayorder, list 0 motion information may be utilized. In some embodiments,how to convert motion information to uni-directional motion vectors maydepend on the low delay check flag.

In some embodiments, the converting process may be invoked right beforethe motion compensation process. In some embodiments, the convertingprocess may be invoked right after the motion candidate list (e.g.,merge list) construction process. In some embodiments, the convertingprocess may be invoked before invoking the adding MVD process in theMMVD process. That is, the adding MVD process follows the design ofuni-prediction instead of bi-prediction. In some embodiments, theconverting process may be invoked before invoking the sample refinementprocess in the PROF process. That is, the adding MVD process follows thedesign of uni-prediction instead of bi-prediction. In some embodiments,the converting process may be invoked before invoking the BIO (a.k.a.BDOF) process. That is, for some cases, BIO may be disabled since it hasbeen converted to uni-prediction. In some embodiments, the convertingprocess may be invoked before invoking the DMVR process. That is, forsome cases, DMVR may be disabled since it has been converted touni-prediction.

Example 17: In some embodiments, how to generate motion candidate listmay depend on block dimension.

In some embodiments, for certain block dimensions, all the motioncandidates derived from spatial blocks and/or temporal block and/or HMVPand/or other kinds of motion candidates may be restricted to beuni-predicted.

In some embodiments, for certain block dimensions, if one motioncandidate derived from spatial blocks and/or temporal block and/or HMVPand/or other kinds of motion candidates is bi-prediction, it may befirstly converted to uni-predicted before being added to the candidatelist.

Example 18: Whether shared merge list is allowed may depend on theencoding mode.

In some embodiments, shared merge list may be disallowed for blockscoded with regular merge mode and may be allowed for blocks coded withIBC mode.

In some embodiments, when one block split from a parent sharing node iscoded with regular merge mode, updating of HMVP tables may be disabledafter encoding/decoding the block.

Example 19: In the above disclosed examples, the block size/width/heightfor a luma block can also be changed to the block size/width/height fora chroma block, such as Cb, Cr, or G/B/R.

Line Buffer Reduction for GBi Mode

Example 20: Whether the GBi weighted index can be inherited or predicted(including CABAC context selection) from a neighboring block or not,depends on the position of the current block.

In some embodiments, the GBi weighted index cannot be inherited orpredicted from a neighboring block which is not in the same Coding TreeUnit (CTU, a.k.a. Largest Coding Unit LCU) as the current block.

In some embodiments, the GBi weighted index cannot be inherited orpredicted from a neighboring block which is not in the same CTU line orCTU row as the current block.

In some embodiments, the GBi weighted index cannot be inherited orpredicted from a neighboring block which is not in the M×N region as thecurrent block. For example, M=N=64. In this case, a tile/slice/pictureis split to multiple un-overlapped M×N regions.

In some embodiments, the GBi weighted index cannot be inherited orpredicted from a neighboring block which is not in the same M×N regionline or M×N region row as the current block. For example, M=N=64. CTUline/row and region line/row are depicted in FIG. 10.

In some embodiments, suppose the top-left corner (or any other position)of the current block is (x,y), the top-left corner (or any otherposition) of the neighboring block is (x′, y′), then it cannot beinherited or predicted from the neighboring block if one of thefollowing conditions is met.

(1) x/M !=x′/M. For example, M=128 or 64.

(2) y/N !=y′/N. For example, N=128 or 64.

(3) ((x/M !=x′/M) && (y/N !=y′/N)). For example, M=N=128 or M=N=64.

(4) ((x/M !=x′/M)∥(y/N !=y′/N)). For example, M=N=128 or M=N=64.

(5) x>>M !=x′>>M. For example, M=7 or 6.

(6) y>>N !=y′>>N. For example, N=7 or 6.

(7) ((x>>M !=x′>>M) && (y>>N !=y′>>N)). For example, M=N=7 or M=N=6.

(8) ((x>>M!=x′>>M)∥(y>>N !=y′>>N)). For example, M=N=7 or M=N=6.

In some embodiments, a flag is signaled in PPS or slice header or tilegroup header or tile to indicate whether GBi can be applied or not in apicture/slice/tile group/tile. In some embodiments, whether GBi is usedand how GBi is used (such as how many candidate weights and the weights'values) may be derived for a picture/slice/tile group/tile. In someembodiments, the derivation may depend on information such as QP,temporal layer, POC distance, etc.

FIG. 10 shows an example of CTU (region) lines. Shaded CTUs (regions)are in one CUT (region) line, Un-shaded CTUs (regions) are in the otherCUT (region) line.

Simplification for Inter-Intra Prediction (IIP)

Example 21: Coding of an intra-prediction mode in an IIP-coded block iscoded is independently from the intra-prediction mode of an IIP-codedneighboring block.

In some embodiments, only intra-prediction mode of an intra-coded blockcan be used in the coding of the intra-prediction mode for an IIP-codedblock, such as, during the MPM list construction process.

In some embodiments, the intra-prediction mode in an IIP-coded block iscoded without mode prediction from any neighboring blocks.

Example 22: the intra-prediction mode of an IIP-coded block may have alower priority than that of an intra-coded block when they are both usedto code the intra-prediction mode of a new IIP-coded block.

In some embodiments, when deriving the MPMs for an IIP-coded block,intra-prediction modes of both IIP-coded block and intra-codedneighboring blocks are utilized. However, intra prediction modes fromintra-coded neighboring blocks may be inserted to the MPM list beforethose from IIP-coded neighboring blocks.

In some embodiments, intra-prediction modes from intra-coded neighboringblocks may be inserted to the MPM list after those from IIP-codedneighboring blocks.

Example 23: The intra-prediction mode in an IIP-coded block can also beused to predict that of an intra-coded block.

In some embodiments, the intra-prediction mode in an IIP-coded block canbe used to derive the MPMs for a normal intra-coded block. In someembodiments, the intra-prediction mode in an IIP-coded block may have alower priority than the intra-prediction mode in an intra-coded blockwhen they are used to derive the MPMs for a normal intra-coded block.

In some embodiments, the intra-prediction mode in an IIP-coded block canalso be used to predict the intra-prediction mode of a normalintra-coded block or IIP-coded block only when one or more of thefollowing conditions is met:

1. the two blocks are in the same CTU line.

2. the two blocks are in the same CTU.

3. the two blocks are in the same M×N region such as M=N=64.

4. the two blocks are in the same M×N region line such as M=N=64.

Example 24: In some embodiments, the MPM construction process for anIIP-coded block should be the same to that for a normal intra-codedblock.

In some embodiments, six MPMs are used for an inter-coded block withinter-intra prediction.

In some embodiments, only partial of MPMs are used for an IIP-codedblock. In some embodiments, the first one is always used. Alternatively,furthermore, there is no need to signal the MPM flag and MPM indexneither. In some embodiments, the first four MPMs may be utilized.Alternatively, furthermore, there is no need to signal the MPM flag butMPM index needs to be signaled.

In some embodiments, each block may select one from the MPM listaccording to the intra prediction modes included in the MPM list, suchas selecting the mode with smallest index compared to a given mode(e.g., planar).

In some embodiments, each block may select a subset of modes from theMPM list and signal the mode index in the subset.

In some embodiments, the contexts used for coding intra MPM modes arereused for coding intra modes in IIP-coded blocks. In some embodiments,different contexts used for coding intra MPM modes are employed forcoding intra modes in IIP-coded blocks.

Example 25: In some embodiments, for angular intra prediction modesexcluding Horizontal and vertical directions, equal weights are utilizedfor the intra prediction block and inter prediction block generated forIIP-coded blocks.

Example 26: In some embodiments, for certain positions, zero weights maybe applied in the IIP coding process.

In some embodiments, zero weights may be applied to the intra predictionblock used in IIP coding process.

In some embodiments, zero weights may be applied to the inter predictionblock used in IIP coding process.

Example 27: In some embodiments, the intra-prediction mode of anIIP-coded block can only be selected as one of the MPMs, no matter whatthe size of the current block is.

In some embodiments, the MPM flag is not signaled and inferred to be 1,no matter what the size of the current block is.

Example 28: For an IIP-coded block, Luma-predict-chroma mode (LM) modeis used instead of derived mode (DM) mode to do the intra-prediction forthe chroma components.

In some embodiments, both DM and LM may be allowed.

In some embodiments, multiple intra prediction modes may be allowed forchroma components.

In some embodiments, whether to allow multiple modes for chromacomponents may depend on the color format. In one example, for 4:4:4color format, the allowed chroma intra prediction modes may be the sameas that for the luma component.

Example 29: Inter-intra prediction may not be allowed in one or morespecific cases as below:

A. w==T1∥h==T1, for example, T1=4

B. w>T1∥h>T1, for example, T1=64

C. (w==T1 && h==T2) 11 (w==T2 && h==T1), for example, T1=4, T2=16.

Example 30: Inter-intra prediction may not be allowed for a block withbi-prediction.

In some embodiments, if the selected merge candidate for an IIP-codedblock uses bi-prediction, it will be converted to a uni-prediction mergecandidate. In some embodiments, only the prediction from reference list0 is retained, and the merge candidate is treated as uni-predictionreferring to reference list 0. In some embodiments, only the predictionfrom reference list 1 is retained, and the merge candidate is treated asuni-prediction referring to reference list 1.

In some embodiments, a restriction is added that the selected mergecandidate shall be an uni-prediction merge candidate. Alternatively, thesignaled merge index for an IIP-coded block indicates the index ofuni-prediction merge candidates (that is, bi-prediction merge candidatesare not counted).

In some embodiments, the merge candidate list construction process usedin Triangular Prediction Mode may be utilized to derive the motioncandidate list for IIP-coded blocks.

Example 31: When Inter-intra prediction is applied, some coding toolsmay be disallowed.

In some embodiments, the Bi-directional Optical flow (BIO) is notapplied for bi-prediction.

In some embodiments, the Overlapped Block Motion Compensation (OBMC) isnot applied.

In some embodiments, decoder side motion vector derivation/refinementprocesses are disallowed.

Example 32: The intra prediction process used in inter-intra predictionmay be different from that used in normal intra-coded blocks.

In some embodiments, the neighboring samples may be filtered indifferent ways. In some embodiments, the neighboring samples are notfiltered before conducting intra-prediction used in inter-intraprediction.

In some embodiments, position-dependent intra prediction samplefiltering process is not conducted for intra-prediction used ininter-intra prediction. In some embodiments, multiline intra-predictionis not allowed in inter-intra prediction. In some embodiments,wide-angle intra-prediction is not allowed in inter-intra prediction.

Example 33: Suppose intra and inter prediction values in hybrid intraand inter prediction are PIntra and Pinter, and the weighting factor arew_intra and w_inter respectively. The prediction value at position (x,y) is calculated as (PIntra(x, y)*w_intra(x, y)+PInter(x, y)*w_inter(x,y)+offset(x, y))>>N, wherein w_intra(x, y)+w_iner(x, y)=2{circumflexover ( )}N, and offset(x, y)=2{circumflex over ( )}(N−1). In oneexample, N=3.

Example 34: In some embodiments, the MPM flags signaled in normalintra-coded block and in the IIP-coded block should share the samearithmetic coding context.

Example 35: In some embodiments, no MPM is needed to code theintra-prediction mode in a IIP-coded block. (Suppose the block width andheight are w and h).

In some embodiments, the four modes {Planar, DC, Vertical, Horizontal}are binarized as 00, 01, 10 and 11 (can be with any mapping rule such as00-Planar, 01-DC, 10-Vertical, 11-Horizontal).

In some embodiments, the four modes {Planar, DC, Vertical, Horizontal}are binarized as 0, 10, 110 and 111 (can be with any mapping rule suchas 0-Planar, 10-DC, 110-Vertical, 111-Horizontal).

In some embodiments, the four modes {Planar, DC, Vertical, Horizontal}are binarized as 1, 01, 001 and 000 (can be with any mapping rule suchas 1-Planar, 01-DC, 001-Vertical, 000-Horizontal).

In some embodiments, only three modes {Planar, DC, Vertical} can be usedwhen W>N*H (N is an integer such as 2) can be used. The three modes arebinarized as 1, 01, 11 (can be with any mapping rule such as 1-Planar,01-DC, 11-Vertical).

In some embodiments, only three modes {Planar, DC, Vertical} can be usedwhen W>N*H (N is an integer such as 2) can be used. The three modes arebinarized as 0, 10, 00 (can be with any mapping rule such as 0-Planar,10-DC, 00-Vertical).

In some embodiments, only three modes {Planar, DC, Horizontal} can beused when H>N*W (N is an integer such as 2) can be used. The three modesare binarized as 1, 01, 11 (can be with any mapping rule such as1-Planar, 01-DC, 11-Horizontal).

In some embodiments, only three modes {Planar, DC, Horizontal} can beused when H>N*W (N is an integer such as 2) can be used. The three modesare binarized as 0, 10, 00 (can be with any mapping rule such as0-Planar, 10-DC, 00-Horizontal).

Example 36: In some embodiments, only DC and Planar modes are used in anIIP-coded block. In some embodiments, one flag is signaled to indicatewhether DC or Planar is used.

Example 37: In some embodiments, IIP is conducted differently fordifferent colour component.

In some embodiments, inter-intra-prediction is not done on chromacomponents (such as Cb and Cr).

In some embodiments, intra-prediction mode for chroma component isdifferent from that for the Luma component in an IIP-coded block. Insome embodiments, DC mode is always used for chroma. In someembodiments, planar mode is always used for chroma.

In some embodiments, LM mode is always used for chroma. In someembodiments, how to conduct IP for different color component may dependon color format (such as 4:2:0 or 4:4:4).

In some embodiments, how to conduct IP for different color component maydepend on block size. For example, Inter-intra-prediction is not done onchroma components (such as Cb and Cr), when width or height of thecurrent block is equal or smaller than 4.

MV Precision Issues

In the following discussion, the precision used for MVs stored forspatial motion prediction is denoted as P1, and the precision used forMVs stored for temporal motion prediction is denoted as P2.

Example 38: P1 and P2 may be the same, or they may be different.

In some embodiments, P1 is 1/16 luma pixel and P2 is ¼ luma pixel. Insome embodiments, P1 is 1/16 luma pixel and P2 is ⅛ luma pixel. In someembodiments, P1 is ⅛ luma pixel and P2 is ¼ luma pixel. In someembodiments, P1 is ⅛ luma pixel and P2 is ⅛ luma pixel. In someembodiments, P2 is 1/16 luma pixel and P1 is ¼ luma pixel. In someembodiments, P2 is 1/16 luma pixel and P1 is ⅛ luma pixel. In someembodiments, P2 is ⅛ luma pixel and P1 is ¼ luma pixel.

Example 39: P1 and P2 may not be fixed. In some embodiments, P1/P2 maybe different for different standard profiles/levels/tiers. In someembodiments, P1/P2 may be different for pictures in different temporallayers. In some embodiments, P1/P2 may be different for pictures withdifferent width/height. In some embodiments, P1/P2 may be signaled fromthe encoder to the decoder in VPS/SPS/PPS/slice header/tile groupheader/tile/CTU/CU.

Example 40: For a MV (MVx, MVy), the precision for MVx and MVy may bedifferent, denoted as Px and Py.

In some embodiments, Px/Py may be different for different standardprofiles/levels/tiers. In some embodiments, Px/Py may be different forpictures in different temporal layers. In some embodiments, Px may bedifferent for pictures with different width. In some embodiments, Py maybe different for pictures with different height. In some embodiments,Px/Py may be signaled from the encoder to the decoder inVPS/SPS/PPS/slice header/tile group header/tile/CTU/CU.

Example 41: Before putting a MV (MVx, MVy) into the storage for temporalmotion prediction, it should be changed to the correct precision.

In some embodiments, MVx=Shift(MVx, P1-P2), MVy=Shift(MVy, P1-P2), ifP1>=P2. In some embodiments, MVx=SignShift(MVx, P1-P2),MVy=SignShift(MVy, P1-P2), if P1>=P2. In some embodiments,MVx=MVx<<(P2-P1), MVy=MVy<<(P2-P1), if P1<P2.

Example 42: Suppose the MV(MVx, MVy) precision is Px and Py, and MVx orMVy is stored by an integer with N bits. The range of MV (MVx, MVy) isMinX<=MVx<=MaxX, and MinY<=MVy<=MaxY.

In some embodiments, MinX may be equal to MinY, or it may not be equalto MinY. In some embodiments, MaxX may be equal to MaxY, or it may notbe equal to MaxY. In some embodiments, {MinX, MaxX} may depend on Px. Insome embodiments, {MinY, MaxY} may depend on Py. In some embodiments,MinX, MaxX, MinY, MaxY} may depend on N. In some embodiments, {MinX,MaxX, MinY, MaxY} may be different for a MV stored for spatial motionprediction and a MV stored for temporal motion prediction.

In some embodiments, {MinX, MaxX, MinY, MaxY} may be different fordifferent standard profiles/levels/tiers. In some embodiments, {MinX,MaxX, MinY, MaxY} may be different for pictures in different temporallayers. In some embodiments, {MinX, MaxX, MinY, MaxY} may be differentfor pictures with different width/height. In some embodiments, {MinX,MaxX, MinY, MaxY} may be signaled from the encoder to the decoder inVPS/SPS/PPS/slice header/tile group header/tile/CTU/CU. In someembodiments, {MinX, MaxX} may be different for pictures with differentwidth. In some embodiments, {MinY, MaxY} may be different for pictureswith different height. In some embodiments, MVx is clipped to [MinX,MaxX] before it is put into the storage for spatial motion prediction.In some embodiments, MVx is clipped to [MinX, MaxX] before it is putinto the storage for temporal motion prediction. In some embodiments,MVy is clipped to [MinY, MaxY] before it is put into the storage forspatial motion prediction. In some embodiments, MVy is clipped to [MinY,MaxY] before it is put into the storage for temporal motion prediction.

Line Buffer Reduction for Affine Merge Mode

Example 43: The affine model (derived CPMVs or affine parameters)inherited by a affine merge candidate from a neighboring block is alwaysa 6-parameter affine model.

In some embodiments, if the neighboring block is coded with the4-parameter affine model, the affine model is still inherited as a6-parameter affine model.

In some embodiments, whether the 4-parameter affine model from aneighboring block is inherited as a 6-parameter affine model or a4-parameter affine model may depends the position of the current block.In some embodiments, the 4-parameter affine model from a neighboringblock is inherited as a 6-parameter affine model if the neighboringblock is not in the same Coding Tree Unit (CTU, a.k.a. Largest CodingUnit LCU) as the current block. In some embodiments, the 4-parameteraffine model from a neighboring block is inherited as a 6-parameteraffine model if the neighboring block is not in the same CTU line or CTUrow as the current block. In some embodiments, the 4-parameter affinemodel from a neighboring block is inherited as a 6-parameter affinemodel if the neighboring block is not in the M×N region as the currentblock. For example, M=N=64. In this case, a tile/slice/picture is splitto multiple un-overlapped M×N regions. In some embodiments, the4-parameter affine model from a neighboring block is inherited as a6-parameter affine model if the neighboring block is not in the same M×Nregion line or M×N region row as the current block. For example, M=N=64.CTU line/row and region line/row are depicted in FIG. 10.

In some embodiments, suppose the top-left corner (or any other position)of the current block is (x,y), the top-left corner (or any otherposition) of the neighboring block is (x′, y′), then the 4-parameteraffine model from a neighboring block is inherited as a 6-parameteraffine model if the neighboring block satisfies one or more of thefollowing conditions:

(a) x/M !=x′/M. For example, M=128 or 64.

(b) y/N !=y′/N. For example, N=128 or 64.

(c) ((x/M !=x′/M) && (y/N !=y′/N)). For example, M=N=128 or M=N=64.

(d) ((x/M !=x′/M)∥(y/N !=y′/N)). For example, M=N=128 or M=N=64.

(e) x>>M !=x′>>M. For example, M=7 or 6.

(f) y>>N !=y′>>N. For example, N=7 or 6.

(g) ((x>>M !=x′>>M) && (y>>N !=y′>>N)). For example, M=N=7 or M=N=6.

(h) ((x>>M !=x′>>M)∥(y>>N !=y′>>N)). For example, M=N=7 or M=N=6.

5. Embodiments

The description below shows an example of how the disclosed technologycan be implemented within the syntax structure of the current VVCstandard. New additions are indicated in bold, and deletions areindicated italics.

5.1 Embodiment #1 (Disabling 4×4 Inter Prediction, and DisablingBi-Prediction for 4×8, 8×4, 4×16 and 16×4 Blocks)

7.3.6.6 Coding Unit Syntax

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, treeType ) {  if(tile_group_type != I | | sps_ibc_enabled_flag ) { if( treeType !=DUAL_TREE_CHROMA && !( cbWidth == 4 && cbHeight == 4 && !sps _(—) ibc_(—) enabled _(—) flag ) )  cu _(—) skip _(—) flag[ x0 ][ y0 ] ae(v) if(cu_skip_flag[ x0 ][ y0 ] = = 0 && tile_group_type != I && !( cbWidth ==4 && cbHeight == 4 ) )  pred_mode_flag ae(v) if( ( ( tile_group_type = =I && cu_skip_flag[ x0 ][ y0 ] = =0 ) | |  ( tile_group_type != I &&CuPredMode[ x0 ][ y0 ] != MODE_INTRA ) ) &&  sps_ibc_enabled_flag && !(cbWidth == 4 && cbHeight == 4 && cu _(—) skip _(—) flag[ x0 ][ y0 ] = =1 ) )  pred_mode_ibc_flag ae(v)  }  if( CuPredMode[ x0 ][ y0 ] = =MODE_INTRA ) { if( sps_pcm_enabled_flag &&  cbWidth >= MinIpcmCbSizeY &&cbWidth <= MaxIpcmCbSizeY &&  cbHeight >= MinIpcmCbSizeY && cbHeight <=MaxIpcmCbSizeY )  pcm _(—) flag[ x0 ][ y0 ] ae(v) if( pcm_flag[ x0 ][ y0] ) {  while( !byte_aligned( ) ) pcm_alignment_zero_bit f(1) pcm_sample( cbWidth, cbHeight, treeType) } else {  if( treeType = =SINGLE_TREE | | treeType = = DUAL_TREE_LUMA ) { if( ( y0 % CtbSizeY ) >0 )  intra_luma_ref_idx[ x0 ][ y0 ] ae(v) if (intra_luma_ref_idx[ x0 ][y0 ] = = 0 &&  ( cbWidth <= MaxTbSizeY | | cbHeight <= MaxTbSizeY ) && ( cbWidth * cbHeight > MinTbSizeY * MinTbSizeY )) intra_subpartitions_mode_flag[ x0 ][ y0 ] ae(v) if(intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 1 &&  cbWidth <=MaxTbSizeY && cbHeight <= MaxTbSizeY )  intra_subpartitions_split_flag[x0 ][ y0 ] ae(v) if( intra_luma_ref_idx[ x0 ][ y0 ] = = 0 && intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 0 )  intra_luma_mpm_flag[x0 ][ y0 ] ae(v) if( intra_luma_mpm_flag[ x0 ][ y0 ] ) intra_luma_mpm_idx[ x0 ][ y0 ] ae(v) else  intra_luma_mpm_remainder[ x0][ y0 ] ae(v)  }  if( treeType = = SINGLE_TREE | | treeType = =DUAL_TREE_CHROMA ) intra_chroma_pred_mode[ x0 ][ y0 ] ae(v) }  } elseif( treeType != DUAL_TREE_CHROMA ) { /* MODE_INTER or MODE_IBC */ if(cu_skip_flag[ x0 ][ y0 ] = = 0 )  merge_flag[ x0 ][ y0 ] ae(v) if(merge_flag[ x0 ][ y0 ] ) {  merge_data( x0, y0, cbWidth, cbHeight ) }else if ( CuPredMode[ x0 ][ y0 ] = = MODE_IBC ) {  mvd_coding( x0, y0,0, 0 )  mvp_l0_flag[ x0 ][ y0 ] ae(v)  if( sps_amvr_enabled_flag && (MvdL0[ x0 ][ y0 ][ 0 ] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ] != 0 ) ) {amvr_precision_flag[ x0 ][ y0 ] ae(v)  } } else {  if( tile_group_type == B ) inter_pred_idc[ x0 ][ y0 ] ae(v)  if( sps_affine_enabled_flag &&cbWidth >= 16 && cbHeight >= 16 ) { inter_affine_flag[ x0 ][ y0 ] ae(v)if( sps_affine_type_flag && inter_affine_flag[ x0 ][ y0 ] ) cu_affine_type_flag[ x0 ][ y0 ] ae(v)  } ... }7.4.7.6 Coding Unit Semanticspred_mode_flag equal to 0 specifies that the current coding unit iscoded in inter prediction mode. pred_mode_flag equal to 1 specifies thatthe current coding unit is coded in intra prediction mode. The variableCuPredMode[xfy] is derived as follows for x=x0 . . . x0+cbWidth−1 andy=y0 . . . y0+cbHeight−1:

-   -   If pred_mod_flag is equal to 0,CuPredMode[x][y] is set equal to        MODE_INTER.    -   Otherwise (pred_mode_flag is equal to 1), CuPredMode[xf][y] is        set equal to MODE_INTRA.        When pred_mode_flag is not present, it is inferred to be equal        to 1 when decoding an I tile group or when decoding a coding        unit with cb Width is equal to 4 and cb Height is equal to 4,        and equal to 0 when decoding a P or B tile group, respectively.        pred_mode_ibc_flag equal to 1 specifies that the current coding        unit is coded in IBC prediction mode. pred_mode_ibc_flag equal        to 0 specifies that the current coding unit is not coded in IBC        prediction mode.        When pred_mode_ibc_flag is not present, it is inferred to be        equal to the value of sps_ibc_enabled_flag when decoding an I        tile group or when decoding a coding unit coded in skip mode and        cbWidth is equal to 4 and cbHeight is equal to 4, and 0 when        decoding a P or B tile group, respectively.        When pred_mode_ibc_flag is equal to 1, the variable        CuPredMode[x]I[y] is set to be equal to MODE_IBC for x=x0 . . .        x0+cbWidth−1 and y=y0 . . . y0+cbHeight−1.        inter_pred_idc[x0][y0] specifies whether list0, list1, or        bi-prediction is used for the current coding unit according to        Table 7-9. The array indices x0, y0 specify the location (x0,        y0) of the top-left luma sample of the considered coding block        relative to the top-left luma sample of the picture.

TABLE 7-9 Name association to inter prediction mode Name ofinter_pred_idc ( cbWidth + cbHeight ) = = 8 | | ( cbWidth + ( cbWidth +cbHeight ) = = 12 | | inter_pred_idc cbHeight ) != 8 ( cbWidth +cbHeight ) = = 20 0 PRED_L0 PRED_L0 1 PRED_L1 PRED_L1 2 PRED_BI n.a.When inter_pred_idc[x0][y0] is not present, it is inferred to be equalto PRED_L0.8.5.2.1 GeneralInputs to this process are:

-   -   a luma location (xCb, yCb) of the top-left sample of the current        luma coding block relative to the top-left luma sample of the        current picture,    -   a variable cbWidth specifying the width of the current coding        block in luma samples,    -   a variable cbHeight specifying the height of the current coding        block in luma samples.        Outputs of this process are:    -   the luma motion vectors in 1/16 fractional-sample accuracy        mvL0[0][0] and mvL1[0][0],    -   the reference indices refIdxL0 and refIdxL1,    -   the prediction list utilization flags predFlagL0[0][0] and        predFlagL1[0][0],    -   the bi-prediction weight index gbiIdx.        Let the variable LX be RefPicList[X], with X being 0 or 1, of        the current picture.        For the derivation of the variables mvL0[0][0] and mvL1[0][0],        refIdxL0 and refIdxL1, as well as predFlagL0[0][0] and        predFlagL1[0][0], the following applies:    -   If merge_flag[xCb][yCb] is equal to 1, the derivation process        for luma motion vectors for merge mode as specified in clause        8.5.2.2 is invoked with the luma location (xCb, yCb), the        variables cbWidth and cbHeight inputs, and the output being the        luma motion vectors mvL0[0][0], mvL1[0][0], the reference        indices refIdxL0, refIdxL1, the prediction list utilization        flags predFlagL0[0][0] and predFlagL1[0][0], and the        bi-prediction weight index gbiIdx.    -   Otherwise, the following applies:        -   For X being replaced by either 0 or 1 in the variables            predFlagLX[0][0], mvLX[0][0] and refIdxLX, in PRED_LX, and            in the syntax elements ref_idx_lX and MvdLX, the following            ordered steps apply:    -   1. The variables refIdxLX and predFlagLX[0][0] are derived as        follows:        -   If inter_pred_idc[xCb][yCb] is equal to PRED_LX or PRED_BI,            refIdxLX=ref_idx_lX[xCb][yCb]  (8-266)            predFlagLX[0][0]=1  (8-267)        -   Otherwise, the variables refIdxLX and predFlagLX[0][0] are            specified by:            refIdxLX=−1  (8-268)            predFlagLX[0][0]=0  (8-269)    -   2. The variable mvdLX is derived as follows:        mvdLX[0]=MvdLX[xCb][yCb][0]  (8-270)        mvdLX[1]=MvdLX[xCb][yCb][1]  (8-271)    -   3. When predFlagLX[0][0] is equal to 1, the derivation process        for luma motion vector prediction in clause 8.5.2.8 is invoked        with the luma coding block location (xCb, yCb), the coding block        width cbWidth, the coding block height cbHeight and the variable        refIdxLX as inputs, and the output being mvpLX.    -   4. When predFlagLX[0][0] is equal to 1, the luma motion vector        mvLX[0][0] is derived as follows:        uLX[0]=(mvpLX[0]+mvdLX[0]+2¹⁸)% 2¹⁸  (8-272)        mvLX[0][0][0]=(uLX[0]>=2¹⁷)?(uLX[0]−2¹⁸):uLX[0]  (8-273)        uLX[1]=(mvpLX[1]+mvdLX[1]+2¹⁸)% 2¹⁸  (8-274)        mvLX[0][0][1]=(uLX[1]>=2¹⁷)?(uLX[1]−2¹⁸):uLX[1]   (8-275)        -   NOTE 1—The resulting values of mvLX[0][0][0] and            mvLX[0][0][1] as specified above will always be in the range            of −2¹⁷ to 2¹⁷−1, inclusive.    -   The bi-prediction weight index gbiIdx is set equal to        gbi_idx[xCb][yCb].        When all of the following conditions are true, refIdxL1 is set        equal to −1, predFlagL1 is set equal to 0, and gbiIdx is set        equal to 0:    -   predFlagL0[0][0] is equal to 1.    -   predFlagL1[0][0] is equal to 1.    -   (cbWidth+cbHeight==8)∥(cbWidth+cbHeight==12)∥(cbWidth+cbHeight==20)        =cbWidth is equal to 4; cbHeight equal to 4.        The updating process for the history-based motion vector        predictor list as specified in clause 8.5.2.16 is invoked with        luma motion vectors mvL0[0][0] and mvL1[0][0], reference indices        refIdxL0 and refIdxL1, prediction list utilization flags        predFlagL0[0][0] and predFlagL1[0][0], and bi-prediction weight        index gbiIdx.        9.5.3.8 Binarization Process for Inter_Pred_Idc        Input to this process is a request for a binarization for the        syntax element inter_pred_idc, the current luma coding block        width cbWidth and the current luma coding block height cbHeight.        Output of this process is the binarization of the syntax        element.        The binarization for the syntax element inter_pred_idc is        specified in Table 9-9.

TABLE 9-9 Binarization for inter_pred_idc Bin string ( cbWidth +cbHeight ) == 8 | | Value of Name of ( cbWidth + ( cbWidth + cbHeight )== 12 | | inter_pred_idc inter_pred_idc cbHeight ) != 8 ( cbWidth +cbHeight ) == 20 0 PRED_L0 00 0 1 PRED_L1 01 1 2 PRED_BI 1 —9.5.4.2.1 General

TABLE 9-10 Assignment of ctxInc to syntax elements with context codedbins inter_pred_idc[ x0 ][ y0 ] ( cbWidth + cbHeight ) != 8 && 4 na nana na ( cbWidth + cbHeight ) != 12 && ( cbWidth + cbHeight ) != 20 ? 7 −( ( 1 + Log2( cbWidth ) + Log2( cbHeight ) ) >> 1 ) : 4

5.2 Embodiment #2 (Disabling 4×4 Inter Prediction)

7.3.6.6 Coding Unit Syntax

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, treeType ) {  if(tile_group_type != I | | sps_ibc_enabled_flag ) { if( treeType !=DUAL_TREE_CHROMA && !( cbWidth == 4 && cbHeight == 4 && !sps _(—) ibc_(—) enabled _(—) flag ) )  cu_skip_flag[ x0 ][ y0 ] ae(v) if(cu_skip_flag[ x0 ][ y0 ] = = 0 && tile_group_type != I && !( cbWidth ==4 && cbHeight == 4 ) )  pred_mode_flag ae(v) if( ( ( tile_group_type = =I && cu_skip_flag[ x0 ][ y0 ] = =0 ) | |  ( tile_group_type != I &&CuPredMode[ x0 ][ y0 ] != MODE_INTRA ) ) &&  sps_ibc_enabled_flag && !(cbWidth == 4 && cbHeight == 4 && cu _(—) skip _(—) flag[ x0 ][ y0 ] = =1 ) )  pred_mode_ibc_flag ae(v)  }  if( CuPredMode[ x0 ][ y0 ] = =MODE_INTRA ) { if( sps_pcm_enabled_flag &&  cbWidth >= MinIpcmCbSizeY &&cbWidth <= MaxIpcmCbSizeY &&  cbHeight >= MinIpcmCbSizeY && cbHeight <=MaxIpcmCbSizeY )  pcm_flag[ x0 ][ y0 ] ae(v) if( pcm_flag[ x0 ][ y0 ] ){  while( !byte_aligned( ) ) pcm_alignment_zero_bit f(1)  pcm_sample(cbWidth, cbHeight, treeType) } else {  if( treeType = = SINGLE_TREE | |treeType = = DUAL_TREE_LUMA ) { if( ( y0 % CtbSizeY ) > 0 ) intra_luma_ref_idx[ x0 ][ y0 ] ae(v) if (intra_luma_ref_idx[ x0 ][ y0 ]= = 0 &&  ( cbWidth <= MaxTbSizeY | | cbHeight <= MaxTbSizeY ) &&  (cbWidth * cbHeight > MinTbSizeY * MinTbSizeY )) intra_subpartitions_mode_flag[ x0 ][ y0 ] ae(v) if(intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 1 &&  cbWidth <=MaxTbSizeY && cbHeight <= MaxTbSizeY )  intra_subpartitions_split_flag[x0 ][ y0 ] ae(v) if( intra_luma_ref_idx[ x0 ][ y0 ] = = 0 && intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 0 )  intra_luma_mpm_flag[x0 ][ y0 ] ae(v) if( intra_luma_mpm_flag[ x0 ][ y0 ] ) intra_luma_mpm_idx[ x0 ][ y0 ] ae(v) else  intra_luma_mpm_remainder[ x0][ y0 ] ae(v)  }  if( treeType = = SINGLE_TREE | | treeType = =DUAL_TREE_CHROMA ) intra_chroma_pred_mode[ x0 ][ y0 ] ae(v) }  } elseif( treeType != DUAL_TREE_CHROMA ) { /* MODE_INTER or MODE_IBC */ if(cu_skip_flag[ x0 ][ y0 ] = = 0 )  merge_flag[ x0 ][ y0 ] ae(v) if(merge_flag[ x0 ][ y0 ] ) {  merge_data( x0, y0, cbWidth, cbHeight ) }else if ( CuPredMode[ x0 ][ y0 ] = = MODE_IBC ) {  mvd_coding( x0, y0,0, 0 )  mvp_l0_flag[ x0 ][ y0 ] ae(v)  if( sps_amvr_enabled_flag && (MvdL0[ x0 ][ y0 ][ 0 ] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ] != 0 ) ) {amvr_precision_flag[ x0 ][ y0 ] ae(v)  } } else {  if( tile_group_type == B ) inter_pred_idc[ x0 ][ y0 ] ae(v)  if( sps_affine_enabled_flag &&cbWidth >= 16 && cbHeight >= 16 ) { inter_affine_flag[ x0 ][ y0 ] ae(v)if( sps_affine_type_flag && inter_affine_flag[ x0 ][ y0 ] ) cu_affine_type_flag[ x0 ][ y0 ] ae(v)  } ... }7.4.7.6 Coding Unit Semanticspred_mode_flag equal to 0 specifies that the current coding unit iscoded in inter prediction mode. pred_mode_flag equal to 1 specifies thatthe current coding unit is coded in intra prediction mode. The variableCuPredMode[xfy] is derived as follows for x=x0 . . . x0+cbWidth−1 andy=y0 . . . y0+cbHeight−1:

-   -   If pred_mod_flag is equal to 0,CuPredMode[x][y] is set equal to        MODE_INTER.    -   Otherwise (pred_mode_flag is equal to 1), CuPredMode[xf][y] is        set equal to MODE_INTRA.        When pred_mode_flag is not present, it is inferred to be equal        to 1 when decoding an I tile group or when decoding a coding        unit with cbWidth is equal to 4 and cbHeight is equal to 4, and        equal to 0 when decoding a P or B tile group, respectively.        pred_mode_ibc_flag equal to 1 specifies that the current coding        unit is coded in IBC prediction mode. pred_mode_ibc_flag equal        to 0 specifies that the current coding unit is not coded in IBC        prediction mode.        When pred_mode_ibc_flag is not present, it is inferred to be        equal to the value of sps_ibc_enabled_flag when decoding an I        tile group or when decoding a coding unit coded in skip mode and        cbWidth is equal to 4 and cbHeight is equal to 4, and 0 when        decoding a P or B tile group, respectively.        When pred_mode_ibc_flag is equal to 1, the variable        CuPredMode[x]I[y] is set to be equal to MODE_IBC for x=x0 . . .        x0+cbWidth−1 and y=y0 . . . y0+cbHeight−1.

5.3 Embodiment #3 (Disabling Bi-Prediction for 4×8, 8×4, 4×16 and 16×4Blocks)

7.4.7.6 Coding Unit Semantics

inter_pred_idc[x0][y0] specifies whether list0, list1, or bi-predictionis used for the current coding unit according to Table 7-9. The arrayindices x0, y0 specify the location (x0, y0) of the top-left luma sampleof the considered coding block relative to the top-left luma sample ofthe picture.

TABLE 7-9 Name association to inter prediction mode Name ofinter_pred_idc ( cbWidth + cbHeight ) = = 8 | | ( cbWidth + ( cbWidth +cbHeight ) = = 12 | | inter_pred_idc cbHeight ) != 8 ( cbWidth +cbHeight ) = = 20 0 PRED_L0 PRED_L0 1 PRED_L1 PRED_L1 2 PRED_BI n.a.When inter_pred_idc[x0][y0] is not present, it is inferred to be equalto PRED_L0.8.5.2.1 GeneralInputs to this process are:

-   -   a luma location (xCb, yCb) of the top-left sample of the current        luma coding block relative to the top-left luma sample of the        current picture,    -   a variable cbWidth specifying the width of the current coding        block in luma samples,    -   a variable cbHeight specifying the height of the current coding        block in luma samples.

Outputs of this process are:

-   -   the luma motion vectors in 1/16 fractional-sample accuracy        mvL0[0][0] and mvL1[0],[0]    -   the reference indices refIdxL0 and refIdxL1,    -   the prediction list utilization flags predFlagL0[0][0] and        predFlagL1[0][0],    -   the bi-prediction weight index gbiIdx.        Let the variable LX be RefPicList[X], with X being 0 or 1, of        the current picture.        For the derivation of the variables mvL0[0][0] and mvL1[0][0],        refIdxL0 and refIdxL1, as well as predFlagL0[0][0] and        predFlagL1[0][0], the following applies:    -   If merge_flag[xCb][yCb] is equal to 1, the derivation process        for luma motion vectors for merge mode as specified in clause        8.5.2.2 is invoked with the luma location (xCb, yCb), the        variables cbWidth and cbHeight inputs, and the output being the        luma motion vectors mvL0[0][0], mvL1[0][0], the reference        indices refIdxL0, refIdxL1, the prediction list utilization        flags predFlagL0[0][0] and predFlagL1[0][0], and the        bi-prediction weight index gbiIdx.    -   Otherwise, the following applies:        -   For X being replaced by either 0 or 1 in the variables            predFlagLX[0][0], mvLX[0][0] and refIdxLX, in PRED_LX, and            in the syntax elements ref_idx_lX and MvdLX, the following            ordered steps apply:    -   5. The variables refIdxLX and predFlagLX[0][0] are derived as        follows:        -   If inter_pred_idc[xCb][yCb] is equal to PRED_LX or PRED_BI,            refIdxLX=ref_idx_lX[xCb][yCb]  (8-266)            predFlagLX[0][0]=1  (8-267)        -   Otherwise, the variables refIdxLX and predFlagLX[0][0] are            specified by:            refIdxLX=−1  (8-268)            predFlagLX[0][0]=0  (8-269)    -   6. The variable mvdLX is derived as follows:        mvdLX[0]=MvdLX[xCb][yCb][0]  (8-270)        mvdLX[1]=MvdLX[xCb][yCb][1]  (8-271)    -   7. When predFlagLX[0][0] is equal to 1, the derivation process        for luma motion vector prediction in clause 8.5.2.8 is invoked        with the luma coding block location (xCb, yCb), the coding block        width cbWidth, the coding block height cbHeight and the variable        refIdxLX as inputs, and the output being mvpLX.    -   8. When predFlagLX[0][0] is equal to 1, the luma motion vector        mvLX[0][0] is derived as follows:        uLX[0]=(mvpLX[0]+mvdLX[0]+2¹⁸)% 2¹⁸  (8-272)        mvLX[0][0][0]=(uLX[0]>=2¹⁷)?(uLX[0]-2¹⁸): uLX[0]  (8-273)        uLX[1]=(mvpLX[1]+mvdLX[1]+2¹⁸)% 2¹⁸  (8-274)        mvLX[0][0][1]=(uLX[1]>=2¹⁷)?(uLX[1]−2¹⁸):uLX[1]   (8-275)        -   NOTE 1—The resulting values of mvLX[0][0][0] and            mvLX[0][0][1] as specified above will always be in the range            of −2¹⁷ to 2¹⁷−1, inclusive.    -   The bi-prediction weight index gbiIdx is set equal to        gbi_idx[xCb][yCb].        When all of the following conditions are true, refIdxL1 is set        equal to −1, predFlagL1 is set equal to 0, and gbiIdx is set        equal to 0:    -   predFlagL0[0][0] is equal to 1.    -   predFlagL1[0][0] is equal to 1.    -   (cbWidth+cbHeight==8) II (cbWidth+cbHeight==12) II        (cbWidth+cbHeight==20)    -   cbWidth is equal to 4; cbHeight equal to 4.        The updating process for the history-based motion vector        predictor list as specified in clause 8.5.2.16 is invoked with        luma motion vectors mvL0[0][0] and mvL1[0][0], reference indices        refIdxL0 and refIdxL1, prediction list utilization flags        predFlagL0[0][0] and predFlagL1[0][0], and bi-prediction weight        index gbiIdx.        9.5.3.8 Binarization Process for Inter_Pred_Idc        Input to this process is a request for a binarization for the        syntax element inter_pred_idc, the current luma coding block        width cbWidth and the current luma coding block height cbHeight.        Output of this process is the binarization of the syntax        element.        The binarization for the syntax element inter_pred_idc is        specified in Table 9-9.

TABLE 9-9 Binarization for inter_pred_idc Bin string ( cbWidth +cbHeight ) = = 8 | | Value of Name of ( cbWidth + ( cbWidth + cbHeight )= = 12 | | inter_pred_idc inter_pred_idc cbHeight ) != 8 ( cbWidth +cbHeight ) = = 20 0 PRED_L0 00 0 1 PRED_L1 01 1 2 PRED_BI 1 —9.5.4.2.1 General

TABLE 9-10 Assignment of ctxInc to syntax elements with context codedbins inter_pred_idc[ x0 ][ y0 ] ( cbWidth + cbHeight ) != 8 && 4 na nana na ( cbWidth + cbHeight ) != 12 && ( cbWidth + cbHeight ) != 20 ? 7 −( ( 1 + Log2( cbWidth ) + Log2( cbHeight ) ) >> 1 ) : 4

Embodiment #4 (Disabling 4×4 Inter Prediction, and DisablingBi-Prediction for 4×8, 8×4 Blocks)

7.3.6.6 Coding Unit Syntax

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, treeType ) {  if(tile_group_type != I | | sps_ibc_enabled_flag ) { if( treeType !=DUAL_TREE_CHROMA && !( cbWidth == 4 && cbHeight == 4 && !sps _(—) ibc_(—) enabled _(—) flag ) )  cu_skip_flag[ x0 ][ y0 ] ae(v) if(cu_skip_flag[ x0 ][ y0 ] = = 0 && tile_group_type != I && !( cbWidth ==4 && cbHeight == 4 ) )  pred_mode_flag ae(v) if( ( ( tile_group_type = =I && cu_skip_flag[ x0 ][ y0 ] = =0 ) | |   ( tile_group_type != I &&CuPredMode[ x0 ][ y0 ] != MODE_INTRA ) ) &&  sps_ibc_enabled_flag && !(cbWidth == 4 && cbHeight == 4 && cu _(—) skip _(—) flag[ x0 ][ y0 ] = =1 ) )  pred_mode_ibc_flag ae(v)  }  if( CuPredMode[ x0 ][ y0 ] = =MODE_INTRA ) { if( sps_pcm_enabled_flag &&  cbWidth >= MinIpcmCbSizeY &&cbWidth <= MaxIpcmCbSizeY &&  cbHeight >= MinIpcmCbSizeY && cbHeight <=MaxIpcmCbSizeY )  pcm_flag[ x0 ][ y0 ] ae(v) if( pcm_flag[ x0 ][ y0 ] ){  while( !byte_aligned( ) ) pcm_alignment_zero_bit f(1)  pcm_sample(cbWidth, cbHeight, treeType) } else {  if( treeType = = SINGLE_TREE | |treeType = = DUAL_TREE_LUMA ) { if( ( y0 % CtbSizeY ) > 0 ) intra_luma_ref_idx[ x0 ][ y0 ] ae(v) if (intra_luma_ref_idx[ x0 ][ y0 ]= = 0 &&  ( cbWidth <= MaxTbSizeY | | cbHeight <= MaxTbSizeY ) &&  (cbWidth * cbHeight > MinTbSizeY * MinTbSizeY )) intra_subpartitions_mode_flag[ x0 ][ y0 ] ae(v) if(intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 1 &&  cbWidth <=MaxTbSizeY && cbHeight <= MaxTbSizeY )  intra_subpartitions_split_flag[x0 ][ y0 ] ae(v) if( intra_luma_ref_idx[ x0 ][ y0 ] = = 0 && intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 0 )  intra_luma_mpm_flag[x0 ][ y0 ] ae(v) if( intra_luma_mpm_flag[ x0 ][ y0 ] ) intra_luma_mpm_idx[ x0 ][ y0 ] ae(v) else  intra_luma_mpm_remainder[ x0][ y0 ] ae(v)  }  if( treeType = = SINGLE_TREE | | treeType = =DUAL_TREE_CHROMA ) intra_chroma_pred_mode[ x0 ][ y0 ] ae(v) }  } elseif( treeType != DUAL_TREE_CHROMA ) { /* MODE_INTER or MODE_IBC */ if(cu_skip_flag[ x0 ][ y0 ] = = 0 )  merge_flag[ x0 ][ y0 ] ae(v) if(merge_flag[ x0 ][ y0 ] ) {  merge_data( x0, y0, cbWidth, cbHeight ) }else if ( CuPredMode[ x0 ][ y0 ] = = MODE_IBC ) {  mvd_coding( x0, y0,0, 0 )  mvp_l0_flag[ x0 ][ y0 ] ae(v)  if( sps_amvr_enabled_flag && (MvdL0[ x0 ][ y0 ][ 0 ] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ] != 0 ) ) {amvr_precision_flag[ x0 ][ y0 ] ae(v)  } } else {  if( tile_group_type == B ) inter_pred_idc[ x0 ][ y0 ] ae(v)  if( sps_affine_enabled_flag &&cbWidth >= 16 && cbHeight >= 16 ) { inter_affine_flag[ x0 ][ y0 ] ae(v)if( sps_affine_type_flag && inter_affine_flag[ x0 ][ y0 ] ) cu_affine_type_flag[ x0 ][ y0 ] ae(v)  } ... }7.4.7.6 Coding Unit Semanticspred_mode_flag equal to 0 specifies that the current coding unit iscoded in inter prediction mode. pred_mode_flag equal to 1 specifies thatthe current coding unit is coded in intra prediction mode. The variableCuPredMode[xfy] is derived as follows for x=x0 . . . x0+cbWidth−1 andy=y0 . . . y0+cbHeight−1:

-   -   If pred_mod_flag is equal to 0,CuPredMode[x][y] is set equal to        MODE_INTER.    -   Otherwise (pred_mode_flag is equal to 1), CuPredMode[x][y] is        set equal to MODE_INTRA.        When pred_mode_flag is not present, it is inferred to be equal        to 1 when decoding an I tile group or when decoding a coding        unit with cbWidth is equal to 4 and cbHeight is equal to 4, and        equal to 0 when decoding a P or B tile group, respectively.        pred_mode_ibc_flag equal to 1 specifies that the current coding        unit is coded in IBC prediction mode. pred_mode_ibc_flag equal        to 0 specifies that the current coding unit is not coded in IBC        prediction mode.        When pred_mode_ibc_flag is not present, it is inferred to be        equal to the value of sps_ibc_enabled_flag when decoding an I        tile group or when decoding a coding unit coded in skip mode and        cbWidth is equal to 4 and cbHeight is equal to 4, and 0 when        decoding a P or B tile group, respectively.        When pred_mode_ibc_flag is equal to 1, the variable        CuPredMode[x][y] is set to be equal to MODE_IBC for x=x0 . . .        x0+cbWidth−1 and y=y0 . . . y0+cbHeight−1.        inter_pred_idc[x0][y0] specifies whether list0, list1, or        bi-prediction is used for the current coding unit according to        Table 7-9. The array indices x0, y0 specify the location (x0,        y0) of the top-left luma sample of the considered coding block        relative to the top-left luma sample of the picture.

TABLE 7-9 Name association to inter prediction mode Name ofinter_pred_idc ( cbWidth + ( cbWidth + cbHeight ) = = 8 | |inter_pred_idc cbHeight ) != 8 ( cbWidth + cbHeight ) = = 12 0 PRED_L0PRED_L0 1 PRED_L1 PRED_L1 2 PRED_BI n.a.When inter_pred_idc[x0][y0] is not present, it is inferred to be equalto PRED_L0.8.5.2.1 GeneralInputs to this process are:

-   -   a luma location (xCb, yCb) of the top-left sample of the current        luma coding block relative to the top-left luma sample of the        current picture,    -   a variable cbWidth specifying the width of the current coding        block in luma samples,    -   a variable cbHeight specifying the height of the current coding        block in luma samples.        Outputs of this process are:    -   the luma motion vectors in 1/16 fractional-sample accuracy        mvL0[0][0] and mvL1[0],[0]    -   the reference indices refIdxL0 and refIdxL1,    -   the prediction list utilization flags predFlagL0[0][0] and        predFlagL1[0][0],    -   the bi-prediction weight index gbiIdx.        Let the variable LX be RefPicList[X], with X being 0 or 1, of        the current picture.        For the derivation of the variables mvL0[0][0] and mvL1[0][0],        refIdxL0 and refIdxL1, as well as predFlagL0[0][0] and        predFlagL1[0][0], the following applies:    -   If merge_flag[xCb][yCb] is equal to 1, the derivation process        for luma motion vectors for merge mode as specified in clause        8.5.2.2 is invoked with the luma location (xCb, yCb), the        variables cbWidth and cbHeight inputs, and the output being the        luma motion vectors mvL0[0][0], mvL1[0][0], the reference        indices refIdxL0, refIdxL1, the prediction list utilization        flags predFlagL0[0][0] and predFlagL1[0][0], and the        bi-prediction weight index gbiIdx.    -   Otherwise, the following applies:        -   For X being replaced by either 0 or 1 in the variables            predFlagLX[0][0], mvLX[0][0] and refIdxLX, in PRED_LX, and            in the syntax elements ref_idx_lX and MvdLX, the following            ordered steps apply:        -   1. The variables refIdxLX and predFlagLX[0][0] are derived            as follows:            -   If inter_pred_idc[xCb][yCb] is equal to PRED_LX or                PRED_BI,                refIdxLX=ref_idx_lX[xCb][yCb]  (8-266)                predFlagLX[0][0]=1  (8-267)            -   Otherwise, the variables refIdxLX and predFlagLX[0][0]                are specified by:                refIdxLX=−1  (8-268)                predFlagLX[0][0]=0  (8-269)        -   2. The variable mvdLX is derived as follows:            mvdLX[0]=MvdLX[xCb][yCb][0]  (8-270)            mvdLX[1]=MvdLX[xCb][yCb][1]  (8-271)        -   3. When predFlagLX[0][0] is equal to 1, the derivation            process for luma motion vector prediction in clause 8.5.2.8            is invoked with the luma coding block location (xCb, yCb),            the coding block width cbWidth, the coding block height            cbHeight and the variable refIdxLX as inputs, and the output            being mvpLX.        -   4. When predFlagLX[0][0] is equal to 1, the luma motion            vector mvLX[0][0] is derived as follows:            uLX[0]=(mvpLX[0]+mvdLX[0]+2¹⁸)% 2¹⁸  (8-272)            mvLX[0][0][0]=(uLX[0]>=2¹⁷)?(uLX[0]−2¹⁸):uLX[0]  (8-273)            uLX[1]=(mvpLX[1]+mvdLX[1]+2¹⁸)% 2¹⁸  (8-274)            mvLX[0][0][1]=(uLX[1]>=2¹⁷)?(uLX[1]−2¹⁸):uLX[1]   (8-275)        -   NOTE 1—The resulting values of mvLX[0][0][0] and            mvLX[0][0][1] as specified above will always be in the range            of −2¹⁷ to 2¹⁷−1, inclusive.    -   The bi-prediction weight index gbiIdx is set equal to        gbi_idx[xCb][yCb].        When all of the following conditions are true, refIdxL1 is set        equal to −1, predFlagL1 is set equal to 0, and gbiIdx is set        equal to 0:    -   predFlagL0[0][0] is equal to 1.    -   predFlagL1[0][0] is equal to 1.    -   (cbWidth+cbHeight==8)∥(cbWidth+cbHeight==12)    -   cbWidth is equal to 4.    -   cbHeight is equal to 4.        The updating process for the history-based motion vector        predictor list as specified in clause 8.5.2.16 is invoked with        luma motion vectors mvL0[0][0] and mvL1[0][0], reference indices        refIdxL0 and refIdxL1, prediction list utilization flags        predFlagL0[0][0] and predFlagL1[0][0], and bi-prediction weight        index gbiIdx.        9.5.3.8 Binarization Process for Inter_Pred_Idc        Input to this process is a request for a binarization for the        syntax element inter_pred_idc, the current luma coding block        width cbWidth and the current luma coding block height cbHeight.        Output of this process is the binarization of the syntax        element.        The binarization for the syntax element inter_pred_idc is        specified in Table 9-9.

TABLE 9-9 Binarization for inter_pred_idc Bin string Value of Name of (cbWidth + ( cbWidth + cbHeight ) = = 8 | | inter_pred_idc inter_pred_idccbHeight ) != 8 ( cbWidth + cbHeight ) = = 12 0 PRED_L0 00 0 1 PRED_L101 1 2 PRED_BI 1 —9.5.4.2.1 General

TABLE 9-10 Assignment of ctxInc to syntax elements with context codedbins inter_pred_idc[ x0 ][ y0 ] ( cbWidth + cbHeight ) != 8 && 4 na nana na ( cbWidth + cbHeight ) != 12 ? 7 − ( ( 1 + Log2( cbWidth ) + Log2(cbHeight ) ) >> 1 ) : 4

Embodiment #5 (Disabling 4×4 Inter Prediction, and DisablingBi-Prediction for 4×8, 8×4 Blocks, Disable Shared Merge List for RegularMerge Mode)

7.3.6.6 Coding Unit Syntax

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, treeType ) {  if(tile_group_type != I | | sps_ibc_enabled_flag ) { if( treeType !=DUAL_TREE_CHROMA && !( cbWidth == 4 && cbHeight == 4 && !sps _(—) ibc_(—) enabled _(—) flag ) )  cu_skip_flag[ x0 ][ y0 ] ae(v) if(cu_skip_flag[ x0 ][ y0 ] = = 0 && tile_group_type != I && !( cbWidth ==4 && cbHeight == 4 ) )  pred_mode_flag ae(v) if( ( ( tile_group_type = =I && cu_skip_flag[ x0 ][ y0 ] = =0 ) | |  ( tile_group_type != I &&CuPredMode[ x0 ][ y0 ] != MODE_INTRA ) ) &&  sps_ibc_enabled_flag && !(cbWidth == 4 && cbHeight == 4 && cu _(—) skip _(—) flag[ x0 ][ y0 ] = =1 ) )  pred_mode_ibc_flag ae(v)  }  if( CuPredMode[ x0 ][ y0 ] = =MODE_INTRA ) { if( sps_pcm_enabled_flag &&  cbWidth >= MinIpcmCbSizeY &&cbWidth <= MaxIpcmCbSizeY &&  cbHeight >= MinIpcmCbSizeY && cbHeight <=MaxIpcmCbSizeY )  pcm_flag[ x0 ][ y0 ] ae(v) if( pcm_flag[ x0 ][ y0 ] ){  while( !byte_aligned( ) ) pcm_alignment_zero_bit f(1)  pcm_sample(cbWidth, cbHeight, treeType) } else {  if( treeType = = SINGLE_TREE | |treeType = = DUAL_TREE_LUMA ) { if( ( y0 % CtbSizeY ) > 0 ) intra_luma_ref_idx[ x0 ][ y0 ] ae(v) if (intra_luma_ref_idx[ x0 ][ y0 ]= = 0 &&  ( cbWidth <= MaxTbSizeY | | cbHeight <= MaxTbSizeY ) &&  (cbWidth * cbHeight > MinTbSizeY * MinTbSizeY )) intra_subpartitions_mode_flag[ x0 ][ y0 ] ae(v) if(intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 1 &&  cbWidth <=MaxTbSizeY && cbHeight <= MaxTbSizeY )  intra_subpartitions_split_flag[x0 ][ y0 ] ae(v) if( intra_luma_ref_idx[ x0 ][ y0 ] = = 0 && intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 0 )  intra_luma_mpm_flag[x0 ][ y0 ] ae(v) if( intra_luma_mpm_flag[ x0 ][ y0 ] ) intra_luma_mpm_idx[ x0 ][ y0 ] ae(v) else  intra_luma_mpm_remainder[ x0][ y0 ] ae(v)  }  if( treeType = = SINGLE_TREE | | treeType = =DUAL_TREE_CHROMA ) intra_chroma_pred_mode[ x0 ][ y0 ] ae(v) }  } elseif( treeType != DUAL_TREE_CHROMA ) { /* MODE_INTER or MODE_IBC */ if(cu_skip_flag[ x0 ][ y0 ] = = 0 )  merge_flag[ x0 ][ y0 ] ae(v) if(merge_flag[ x0 ][ y0 ] ) {  merge_data( x0, y0, cbWidth, cbHeight ) }else if ( CuPredMode[ x0 ][ y0 ] = = MODE_IBC ) {  mvd_coding( x0, y0,0, 0 )  mvp_l0_flag[ x0 ][ y0 ] ae(v)  if( sps_amvr_enabled_flag && (MvdL0[ x0 ][ y0 ][ 0 ] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ] != 0 ) ) {amvr_precision_flag[ x0 ][ y0 ] ae(v)  } } else {  if( tile_group_type == B ) inter_pred_idc[ x0 ][ y0 ] ae(v)  if( sps_affine_enabled_flag &&cbWidth >= 16 && cbHeight >= 16 ) { inter_affine_flag[ x0 ][ y0 ] ae(v)if( sps_affine_type_flag && inter_affine_flag[ x0 ][ y0 ] ) cu_affine_type_flag[ x0 ][ y0 ] ae(v)  } ... }7.4.7.6 Coding Unit Semanticspred_mode_flag equal to 0 specifies that the current coding unit iscoded in inter prediction mode. pred_mode_flag equal to 1 specifies thatthe current coding unit is coded in intra prediction mode. The variableCuPredMode[xfy] is derived as follows for x=x0 . . . x0+cbWidth−1 andy=y0 . . . y0+cbHeight−1:

-   -   If pred_mode_flag is equal to 0,CuPredMode[x][y] is set equal to        MODE_INTER.    -   Otherwise (pred_mode_flag is equal to 1), CuPredMode[xf][y] is        set equal to MODE_INTRA.        When pred_mode_flag is not present, it is inferred to be equal        to 1 when decoding an I tile group or when decoding a coding        unit with cbWidth is equal to 4 and cbHeight is equal to 4, and        equal to 0 when decoding a P or B tile group, respectively.        pred_mode_ibc_flag equal to 1 specifies that the current coding        unit is coded in IBC prediction mode. pred_mode_ibc_flag equal        to 0 specifies that the current coding unit is not coded in IBC        prediction mode.        When pred_mode_ibc_flag is not present, it is inferred to be        equal to the value of sps_ibc_enabled_flag when decoding an I        tile group or when decoding a coding unit coded in skip mode and        cbWidth is equal to 4 and cbHeight is equal to 4, and 0 when        decoding a P or B tile group, respectively.        When pred_mode_ibc_flag is equal to 1, the variable        CuPredMode[x]I[y] is set to be equal to MODE_IBC for x=x0 . . .        x0+cbWidth−1 and y=y0 . . . y0+cbHeight−1.        inter_pred_idc[x0][y0] specifies whether list0, list1, or        bi-prediction is used for the current coding unit according to        Table 7-9. The array indices x0, y0 specify the location (x0,        y0) of the top-left luma sample of the considered coding block        relative to the top-left luma sample of the picture.

TABLE 7-9 Name association to inter prediction mode Name ofinter_pred_idc ( cbWidth + ( cbWidth + cbHeight ) = = 8 | |inter_pred_idc cbHeight ) != 8 ( cbWidth + cbHeight ) = = 12 0 PRED_L0PRED_L0 1 PRED_L1 PRED_L1 2 PRED_BI n.a.When inter_pred_idc[x0][y0] is not present, it is inferred to be equalto PRED_L0.8.5.2.1 GeneralInputs to this process are:

-   -   a luma location (xCb, yCb) of the top-left sample of the current        luma coding block relative to the top-left luma sample of the        current picture,    -   a variable cbWidth specifying the width of the current coding        block in luma samples,    -   a variable cbHeight specifying the height of the current coding        block in luma samples.

Outputs of this process are:

-   -   the luma motion vectors in 1/16 fractional-sample accuracy        mvL0[0][0] and mvL1[0],[0]    -   the reference indices refIdxL0 and refIdxL1,    -   the prediction list utilization flags predFlagL0[0][0] and        predFlagL1[0][0],    -   the bi-prediction weight index gbiIdx.        Let the variable LX be RefPicList[X], with X being 0 or 1, of        the current picture.        For the derivation of the variables mvL0[0][0] and mvL1[0][0],        refIdxL0 and refIdxL1, as well as predFlagL0[0][0] and        predFlagL1[0][0], the following applies:    -   If merge_flag[xCb][yCb] is equal to 1, the derivation process        for luma motion vectors for merge mode as specified in clause        8.5.2.2 is invoked with the luma location (xCb, yCb), the        variables cbWidth and cbHeight inputs, and the output being the        luma motion vectors mvL0[0][0], mvL1[0][0], the reference        indices refIdxL0, refIdxL1, the prediction list utilization        flags predFlagL0[0][0] and predFlagL1[0][0], and the        bi-prediction weight index gbiIdx.    -   Otherwise, the following applies:        -   For X being replaced by either 0 or 1 in the variables            predFlagLX[0][0], mvLX[0][0] and refIdxLX, in PRED_LX, and            in the syntax elements ref_idx_lX and MvdLX, the following            ordered steps apply:            -   5. The variables refIdxLX and predFlagLX[0][0] are                derived as follows:                -   If inter_pred_idc[xCb][yCb] is equal to PRED_LX or                    PRED_BI,                    refIdxLX=ref_idx_lX[xCb][yCb]  (8-266)                    predFlagLX[0][0]=1  (8-267)                -   Otherwise, the variables refIdxLX and                    predFlagLX[0][0] are specified by:                    refIdxLX=−1  (8-268)                    predFlagLX[0][0]=0  (8-269)            -   6. The variable mvdLX is derived as follows:                mvdLX[0]=MvdLX[xCb][yCb][0]  (8-270)                mvdLX[1]=MvdLX[xCb][yCb][1]  (8-271)            -   7. When predFlagLX[0][0] is equal to 1, the derivation                process for luma motion vector prediction in clause                8.5.2.8 is invoked with the luma coding block location                (xCb, yCb), the coding block width cbWidth, the coding                block height cbHeight and the variable refIdxLX as                inputs, and the output being mvpLX.            -   8. When predFlagLX[0][0] is equal to 1, the luma motion                vector mvLX[0][0] is derived as follows:                uLX[0]=(mvpLX[0]+mvdLX[0]+2¹⁸)% 2¹⁸  (8-272)                mvLX[0][0][0]=(uLX[0]>=2¹⁷)?(uLX[0]−2¹⁸):uLX[0]  (8-273)                uLX[1]=(mvpLX[1]+mvdLX[1]+2¹⁸)% 2¹⁸  (8-274)                mvLX[0][0][1]=(uLX[1]>=2¹⁷)?(uLX[1]−2¹⁸):uLX[1]  (8-275)            -   NOTE 1—The resulting values of mvLX[0][0][0] and                mvLX[0][0][1] as specified above will always be in the                range of −2¹⁷ to 2¹⁷−1, inclusive.        -   The bi-prediction weight index gbiIdx is set equal to            gbi_idx[xCb][yCb].            When all of the following conditions are true, refIdxL1 is            set equal to −1, predFlagL1 is set equal to 0, and gbiIdx is            set equal to 0:    -   predFlagL0[0][0] is equal to 1.    -   predFlagL1[0][0] is equal to 1.    -   (cbWidth+cbHeight==8)∥(cbWidth+cbHeight==12)    -   cbWidth is equal to 4.    -   cbHeight is equal to 4.        The updating process for the history-based motion vector        predictor list as specified in clause 8.5.2.16 is invoked with        luma motion vectors mvL0[0][0] and mvL1[0][0], reference indices        refIdxL0 and refIdxL1, prediction list utilization flags        predFlagL0[0][0] and predFlagL1[0][0], and bi-prediction weight        index gbiIdx.        8.5.2.2 Derivation Process for Luma Motion Vectors for Merge        Mode        This process is only invoked when merge_flag[xCb][yPb] is equal        to 1, where (xCb, yCb) specify the top-left sample of the        current luma coding block relative to the top-left luma sample        of the current picture.        Inputs to this process are:    -   a luma location (xCb, yCb) of the top-left sample of the current        luma coding block relative to the top-left luma sample of the        current picture,    -   a variable cbWidth specifying the width of the current coding        block in luma samples,    -   a variable cbHeight specifying the height of the current coding        block in luma samples.        Outputs of this process are:    -   the luma motion vectors in 1/16 fractional-sample accuracy        mvL0[0][0] and mvL1[0][0],    -   the reference indices refIdxL0 and refIdxL1,    -   the prediction list utilization flags predFlagL0[0][0] and        predFlagL1[0][0],    -   the bi-prediction weight index gbiIdx.        The bi-prediction weight index gbiIdx is set equal to 0.        The variables xSmr, ySmr, smrWidth, smrHeight, and        smrNumHmvpCand are derived as follows:        xSmr=IsInSmr[xCb][yCb]?SmrX[xCb][yCb]: xCb  (8-276)        ySmr=IsInSmr[xCb][yCb]?SmrY[xCb][yCb]: yCb  (8-277)        smrWidth=IsInSmr[xCb][yCb]?SmrW[xCb][yCb]cbWidth  (8-278)        smrHeight=IsInSmr[xCb][yCb]?SmrH[xCb][yCb]cbHeight  (8-279)        smrNumHmvpCand=IsInSmr[xCb][yCb]?NumHmvpSmrCand:        NumHmvpCand  (8-280)        8.5.2.6 Derivation Process for History-Based Merging Candidates        Inputs to this process are:    -   a merge candidate list mergeCandList,    -   a variable isInSmr specifying whether the current coding unit is        inside a shared merging candidate region,    -   the number of available merging candidates in the list        numCurrMergeCand.        Outputs to this process are:    -   the modified merging candidate list mergeCandList,    -   the modified number of merging candidates in the list        numCurrMergeCand.        The variables isPrunedA₁ and isPrunedB₁ are both set equal to        FALSE.        The array smrHmvpCandList and the variable smrNumHmvpCand are        derived as follows:        smrHmvpCandList=isInSmr?HmvpSmrCandList: HmvpCandList  (8-353)        smrNumHmvpCand=isInSmr?NumHmvpSmrCand: NumHmvpCand  (8-354)        For each candidate in smrHmvpCandList[hMvpIdx] with index        hMvpIdx=1 . . . smrNumHmvpCand, the following ordered steps are        repeated until numCurrMergeCand is equal to (MaxNumMergeCand−1):    -   1. The variable sameMotion is derived as follows:        -   If all of the following conditions are true for any merging            candidate N with N being A₁ or B₁, sameMotion and isPrunedN            are both set equal to TRUE:            -   hMvpIdx is less than or equal to 2.            -   The candidate smrHmvpCandList[smrNumHmvpCand−hMvpIdx] is                equal to the merging candidate N.            -   isPrunedN is equal to FALSE.        -   Otherwise, sameMotion is set equal to FALSE.    -   2. When sameMotion is equal to FALSE, the candidate        smrHmvpCandList[smrNumHmvpCand−hMvpIdx] is added to the merging        candidate list as follows:        mergeCandList[numCurrMergeCand++]smrHmvpCandList[smrNumHmvpCand        −hMvpIdx]  (8-355)        9.5.3.8 Binarization Process for Inter_Pred_Idc        Input to this process is a request for a binarization for the        syntax element inter_pred_idc, the current luma coding block        width cbWidth and the current luma coding block height cbHeight.        Output of this process is the binarization of the syntax        element.        The binarization for the syntax element inter_pred_idc is        specified in Table 9-9.

TABLE 9-9 Binarization for inter_pred_idc Bin string Value of Name of (cbWidth + ( cbWidth + cbHeight ) = = 8 | | inter_pred_idc inter_pred_idccbHeight ) != 8 ( cbWidth + cbHeight ) = = 12 0 PRED_L0 00 0 1 PRED_L101 1 2 PRED_BI 1 —9.5.4.2.1 General

TABLE 9-10 Assignment of ctxInc to syntax elements with context codedbins inter_pred_idc[ x0 ][ y0 ] ( cbWidth + cbHeight ) != 8 && 4 na nana na ( cbWidth + cbHeight ) != 12 ? 7 − ( ( 1 + Log2( cbWidth ) + Log2(cbHeight ) ) >> 1 ) : 4

FIG. 11 is a block diagram of a video processing apparatus 1100. Theapparatus 1100 may be used to implement one or more of the methodsdescribed herein. The apparatus 1100 may be embodied in a smartphone,tablet, computer, Internet of Things (IoT) receiver, and so on. Theapparatus 1100 may include one or more processors 1102, one or morememories 1104 and video processing hardware 1106. The processor(s) 1102may be configured to implement one or more methods described in thepresent document. The memory (memories) 1104 may be used for storingdata and code used for implementing the methods and techniques describedherein. The video processing hardware 1106 may be used to implement, inhardware circuitry, some techniques described in the present document.

FIG. 12 is a flowchart for an example method 1200 of video processing.The method 1200 includes determining (1202) a size restriction between arepresentative motion vector of a current video block that is affinecoded and motion vectors of sub-blocks of the current video block andperforming (1204), by using the size restriction, a conversion between abitstream representation and pixel values of the current video block orthe subblocks.

In the present document, the term “video processing” may refer to videoencoding, video decoding, video compression or video decompression. Forexample video compression algorithms may be applied during conversionfrom pixel representation of a video to a corresponding bitstreamrepresentation or vice versa. The bitstream representation of a currentvideo block may, for example, correspond to bits that are eitherco-located or spread in different places within the bitstream, as isdefined by the syntax. For example, a macroblock may be encoded in termsof transformed and coded error residual values and also using bits inheaders and other fields in the bitstream.

It will be appreciated that the disclosed techniques are useful toimplement embodiments in which implementation complexity of the videoprocessing is reduced by reduced memory requirements or line buffer sizerequirements. Some presently disclosed techniques may be described usingthe following clause-based description.

1. A method of video processing, comprising:

-   -   determining a size restriction between a representative motion        vector of a current video block that is affine coded and motion        vectors of sub-blocks of the current video block; and    -   performing, by using the size restriction, a conversion between        a bitstream representation and pixel values of the current video        block or the subblocks.

2. The method of clause 1, wherein the performing the conversionincludes generating the bitstream representation from the pixel values.

3. The method of clause 1, wherein the performing the conversionincludes generating the pixel values from the bitstream representation.

4. The method of any of clauses 1 to 3, wherein the size restrictioncomprises constraining values of motion vectors (MVx, MVy) of asub-block according to: MVx>=MV′x-DH0 and MVx<=MV′x+DH1 andMVy>=MV′y-DV0 and MVy<=MV′y+DV1, where MV′=(MV′x, MV′y);

-   -   wherein MV′ represents the representative motion vector; and        wherein DH0, DH1, DV0 and DV1 represent positive numbers.

5. The method of clause 4, wherein the size restriction includes atleast one of the following:

-   -   i. DH0 is equal to DH1 or DV0 is equal to DV1    -   ii. DH0 is equal to DV0 or DH1 is equal to DV1    -   iii. DH0 and DH1 are different or DV0 and DV1 are different    -   iv. DH0, DH1, DV0 and DV1 are signaled in the bitstream        representation at a video parameter set level or a sequence        parameter set level or a picture parameter set level or a slice        header level or a tile group header level or a tile level or a        coding tree unit level or a coding unit level or a prediction        unit level    -   v. DH0, DH1, DV0 and DV1 are a function of a mode of the video        processing    -   vi. DH0, DH1, DV0 and DV1 depend on a width and a height of the        current video block    -   vii. DH0, DH1, DV0 and DV1 depend on whether the current video        block is coded using uni-prediction or bi-prediction    -   viii. DH0, DH1, DV0 and DV1 depend on a position of the        sub-block.

6. The method of any of clauses 1 to 5, wherein the representativemotion vector corresponds to a control point motion vector of thecurrent video block.

7. The method of any of clauses 1 to 5, wherein the representativemotion vector corresponds to a motion vector for a corner sub-block ofthe current video block.

8. The method of any of clauses 1 to 7, wherein a precision used for themotion vectors of the sub-blocks and the representative motion vectorcorresponds to motion vector signaling precision in the bitstreamrepresentation.

9. The method of any of clauses 1 to 7, wherein a precision used for themotion vectors of the sub-blocks and the representative motion vectorcorresponds to a storage precision for storing the motion vectors.

10. A method of video processing, comprising:

-   -   determining for a current video block that is affine coded, one        or more sub-blocks of the current video block, wherein each        sub-block has a size of M×N pixels, where M and N are multiples        of 2 or 4;    -   conforming motion vectors of the sub-blocks to a size        restriction; and    -   performing, conditionally based on a trigger, by using the size        restriction, a conversion between a bitstream representation and        pixel values of the current video block.

11. The method of clause 10, wherein the performing the conversionincludes generating the bitstream representation from the pixel values.

12. The method of clause 10, wherein the performing the conversionincludes generating the pixel values from the bitstream representation.

13. The method of any of clauses 10 to 12, wherein the size restrictionlimits a maximum difference between integer parts of sub-block motionvectors of the current video block is less than or equal to K pixels,where K is an integer.

14. The method of any of clauses 10-13, wherein method is applied onlyin cases where the current video block is coded using bi-prediction.

15. The method of any of clauses 10-13, wherein method is applied onlyin cases where the current video block is coded using uni-prediction.

16. The method of any of clauses 10-13, wherein values of M, N or K area function of uni-prediction or bi-prediction mode of the current videoblock.

17. The method of any of clauses 10-13, wherein values of M, N or K area function of a height or a width of the current video block.

18. The method of any of clauses 10 to 17, wherein the trigger isincluded in the bitstream representation at a video parameter set levelor a sequence parameter set level or a picture parameter set level or aslice header level or a tile group header level or a tile level or acoding tree unit level or a coding unit level or a prediction unitlevel.

19. The method of clause 18, wherein the trigger signals values of M, Nor K.

20. The method of any of clauses 10 to 19, wherein the one or moresub-blocks of the current video block are calculated based on a type ofaffine coding used for the current video block.

21. The method of clause 20, wherein two different methods are used forcalculating sub-blocks of uni-prediction and bi-prediction affineprediction modes.

22. The method of clause 21, wherein, in case that the current videoblock is a bi-predicted affine block, widths or heights of sub-blocksfrom different reference lists are different.

23. The method of any of clauses 20-22, wherein the one or moresub-blocks correspond to luma component.

24. The method of any of clauses 10 to 23, wherein a width and a heightof one of the one or more sub-blocks is determined using a motion vectordifference between motion vector values of the current video block andthat of the one of the one or more sub-blocks.

25. The method of any of clauses 20 to 23, wherein the calculating isbased on a pixel precision signaled in the bitstream representation.

26. A method of video processing, comprising:

-   -   determining that a current video block satisfies a size        condition; and    -   performing, based on the determining, a conversion between a        bitstream representation and pixel values of the current video        block by excluding bi-prediction encoding mode for the current        video block.

27. A method of video processing, comprising:

-   -   determining that a current video block satisfies a size        condition; and    -   performing, based on the determining, a conversion between a        bitstream representation and pixel values of the current video        block wherein an inter prediction mode is signaled in the        bitstream representation according to the size condition.

28. A method of video processing, comprising:

-   -   determining that a current video block satisfies a size        condition; and    -   performing, based on the determining, a conversion between a        bitstream representation and pixel values of the current video        block wherein a generation of merge candidate list during the        conversion is dependent on the size condition.

29. A method of video processing, comprising:

-   -   determining that a child coding unit of a current video block        satisfies a size condition; and    -   performing, based on the determining, a conversion between a        bitstream representation and pixel values of the current video        block, wherein a coding tree splitting process used to generate        the child coding unit is dependent on the size condition.

30. The method of any of clauses 26 to 29, wherein the size condition isone of the following, where w is a width and h is a height:

-   -   (a) w is equal to T1 and h is equal to T2, or h is equal to T1        and w is equal to T2;    -   (b) w is equal to T1 and h is not greater than T2, or h is equal        to T1 and w is not greater than T2;    -   (c) w is not greater than T1 and h is not greater than T2, or h        is not greater than T1 and w is not greater than T2.

31. The method of clause 30, wherein T1=8 and T2=8 or T1=8, T2=4, orT1=4 and T2=4, or T1=4 and T2=16.

32. The method of any of clauses 26 to 29 wherein the conversionincludes generating the bitstream representation from pixel values ofthe current video block or generating pixel values of the current videoblock from the bitstream representation.

33. A method of video processing, comprising:

-   -   determining, a weight index for a generalized bi-prediction        (GBi) process for a current video block based on a position of        the current video block; and    -   performing a conversion between the current video block and a        bitstream representation thereof using the weight index to        implement the GBi process.

34. The method of any clause 33, wherein the conversion includesgenerating the bitstream representation from pixel values of the currentvideo block or generating pixel values of the current video block fromthe bitstream representation.

35. The method of any of clauses 33 or 34, wherein the determiningincludes, for the current video block in a first position, inheriting orpredicting another weight index of a neighboring block, and for thecurrent video block in a second position, calculating the GBI withoutinheriting from the neighboring block.

36. The method of clause 35, wherein the second position comprises thecurrent video block located in a different coding tree unit than theneighboring block.

37. The method of clause 35, wherein the second position corresponds tothe current video block being in a different coding tree unit line or adifferent coding tree unit row than the neighboring block.

38. A method of video processing, comprising:

-   -   determining that a current video block is coded as an        intra-inter prediction (IIP) coded block; and    -   performing a conversion between the current video block and a        bitstream representation thereof using a simplification rule for        determining an intra-prediction mode or a most probable mode        (MPM) for the current video block.

39. The method of clause 38, wherein the conversion includes generatingthe bitstream representation from pixel values of the current videoblock or generating pixel values of the current video block from thebitstream representation.

40. The method of any of clauses 38-39, wherein the simplification rulespecifies determining an intra-prediction coding mode of a current videoblock that is intra-inter prediction (IIP) coded to be independent fromanother intra-prediction coding mode of a neighboring video block.

41. The method of any of clauses 38 to 39, wherein the intra-predictioncoding mode is represented in the bitstream representation using acoding that is independent of that of neighboring blocks.

42. The method of any of clauses 38 to 40, wherein the simplificationrule specifies to prioritize selection to favor coding mode of anintra-coded block over that of an intra-prediction coded block.

43. The method of clause 38, wherein the simplification rule specifiesthe determining the MPM by inserting intra prediction modes fromintra-coded neighboring blocks before inserting intra prediction modesfrom IIP coded neighboring blocks.

44. The method of clause 38, wherein the simplification rule specifiesto use a same construction process for the determining the MPM as usedfor another normal intra-coded block.

45. A method of video processing, comprising:

-   -   determining that a current video block meets a simplification        criterion; and    -   performing a conversion between the current video block and a        bitstream representation by disabling use of inter-intra        prediction mode for the conversion or by disabling additional        coding tools used for the conversion.

46. The method of clause 45, wherein the conversion includes generatingthe bitstream representation from pixel values of the current videoblock or generating pixel values of the current video block from thebitstream representation.

47. The method of any of clauses 45-46, wherein the simplificationcriterion includes that a width or a height of the current video blockis equal to T1, where T1 is an integer.

48. The method of any of clauses 45-46, wherein the simplificationcriterion includes that a width or a height of the current video blockis greater than T1, where T1 is an integer.

49. The method of any of clauses 45-46, wherein the simplificationcriterion includes that a width of the current video block is equal toT1 and a height of the current video block is equal to T2.

48. The method of any of clauses 45-46, wherein the simplificationcriterion specifies that the current video block uses a bi-predictionmode.

49. The method of any of clauses 45-46, wherein the additional codingtools include bi-directional optical flow (BIG) coding.

50. The method of any of clauses 45-46, wherein the additional codingtools include overlapped block motion compensation mode.

51. A method of video processing, comprising:

-   -   performing a conversion between a current video block and a        bitstream representation for the current video block using a        motion vector based encoding process, wherein:

(a) a precision P1 is used for storing spatial motion prediction resultsand a precision P2 is used for storing temporal motion predictionresults during the conversion process, wherein P1 and P2 are fractionalnumbers, or

(b) a precision Px is used for storing x-motion vectors and a precisionPy is used for storing y-motion vectors, wherein Px and Py arefractional numbers.

52. The method of clause 51, wherein P1, P2, Px and Py are differentnumbers.

53. The method of clause 52, wherein:

P1 is 1/16 luma pixel and P2 is ¼ luma pixel, or

P1 is 1/16 luma pixel and P2 is ⅛ luma pixel, or

P1 is ⅛ luma pixel and P2 is ¼ luma pixel, or

P1 is ⅛ luma pixel and P2 is ⅛ luma pixel, or

P2 is 1/16 luma pixel and P1 is ¼ luma pixel, or

P2 is 1/16 luma pixel and P1 is ⅛ luma pixel, or

P2 is ⅛ luma pixel and P1 is ¼ luma pixel.

54. The method of clauses 51-52, wherein P1 and P2 are different fordifferent pictures in different temporal layers that are included in thebitstream representation.

55. The method of clauses 51-52, wherein a computed motion vector isprocessed through a precision correction process prior to storing as thetemporal motion prediction.

56. The method of clauses 51-52, wherein the storing includes storingthe x-motion vectors and the y-motion vectors as an N bit integer, andwherein a range of values of x-motion vectors is [MinX, MaxX] and arange of values of y-motion vectors is [MinY, MaxY], wherein the rangessatisfy one or more of:

a. MinX is equal to MinY,

b. MaxX is equal to MaxY,

c. {MinX, MaxX} depend on Px;

d. {MinY, MaxY} depend on Py;

e. {MinX, MaxX, MinY, MaxY} depend on N.

f. {MinX, MaxX, MinY, MaxY} are different for an MV stored for spatialmotion prediction and another MV stored for temporal motion prediction.

g. {MinX, MaxX, MinY, MaxY} are different for pictures in differenttemporal layers.

h. {MinX, MaxX, MinY, MaxY} are different for pictures with differentwidths or heights.

i. {MinX, MaxX} are different for pictures with different width.

j. {MinY, MaxY} are different for pictures with different height.

k. MVx is clipped to [MinX, MaxX] prior to storing for spatial motionprediction.

l. MVx is clipped to [MinX, MaxX] prior to storing for temporal motionprediction.

m. MVy is clipped to [MinY, MaxY] prior to storing for spatial motionprediction.

n. MVy is clipped to [MinY, MaxY] prior to storing for temporal motionprediction.

59. A method of video processing, comprising: interpolating, a smallsub-block of W1×H1 size within a large sub-block of W2×H2 size of acurrent video block by fetching a (W2+N−1−PW)*(H2+N−1−PH) block, pixelpadding the fetched block, performing boundary pixel repeating on thepixel padded block and obtaining pixel values of the small sub-block,wherein W1, W2, H1, H2, and PW and PH are integers; and performing aconversion between the current video block and a bitstreamrepresentation of the current video block using the interpolated pixelvalues of the small sub-block.

60. The method of clause 59, wherein the conversion includes generatingthe current video block from the bitstream representation or generatingthe bitstream representation from the current sub-block.

61. The method of any of clauses 59-60, wherein W2=H2=8, W1=H1=4 andPW=PH=0.

62. A method of video processing, comprising:

-   -   performing, during a conversion of a current video block of W×H        dimension and a bitstream representation of the current video        block, a motion compensation operation by fetching        (W+N−1−PW)*(W+N−1−PH) reference pixels and padding reference        pixels outsize the fetched reference pixels during the motion        compensation operation; and    -   performing a conversion between the current video block and a        bitstream representation of the current video block using a        result of the motion compensation operation, wherein W, H, N, PW        and PH are integers.

63. The method of clause 62, wherein the conversion includes generatingthe current video block from the bitstream representation or generatingthe bitstream representation from the current sub-block.

64. The method of any of clauses 62-63, wherein the padding includesrepeating left or right boundaries of the fetched pixels.

65. The method of any of clauses 62-63, wherein the padding includesrepeating top or bottom boundaries of the fetched pixels.

66. The method of any of clauses 62-63, wherein the padding includessetting pixel values to a constant.

67. The method of clause 38, wherein the rule specifies that a samearithmetic coding context is used during the conversion as used forother intra-coded blocks.

68. The method of clause 38, wherein the conversion of the current videoblock excludes using the MPM for the current video block.

69. The method of clause 38, wherein the simplification rule specifiesto use only DC and planar mode for the bitstream representation of thecurrent video block that is the IP coded block.

70. The method of clause 38, wherein the simplification rule specifiesdifferent intra-prediction modes for luma and chroma components.

71. The method of clause 44, wherein a subset of the MPMs are used forthe current video block that is IIP coded.

72. The method of clause 38, wherein the simplification rule indicatesthat the MPM is selected based on an intra prediction mode included in aMPM list.

73. The method of clause 38, wherein the simplification rule indicatesthat a subset of MPMs are to be selected from a MPM list, and to signala mode index associated with the subset.

74. The method of clause 38, wherein a context used for coding intra MPMmodes are used for coding intra mode for the current video block that isIIP coded.

75. The method of clause 44, wherein equal weights are used for anintra-prediction block and an inter-prediction block that are generatedfor the current video block, the current video block being an IIP codedblock.

76. The method of clause 44, wherein zero weights are used for positionsin an IIP coding process for the current video block.

77. The method of clause 77, wherein the zero weights are applied to anintra prediction block used in the IIP coding process.

78. The method of clause 77, wherein the zero weights are applied to aninter prediction block used in the IIP coding process.

79. A method of video processing, comprising:

-   -   determining, based on a size of a current video block, that        bi-prediction or uni-prediction of the current video block is        disallowed; and    -   performing, based on the determining, a conversion between a        bitstream representation and pixel values of the current video        block by disabling bi-prediction or uni-prediction mode. For        example, disallowed modes are not used either for encoding or        decoding the current video block. The conversion operation may        represent either video coding or compression, or video decoding        or decompression.

80. The method of clause 79, wherein the current video block is 4×8, anddetermining includes determining that bi-prediction is disallowed. Otherexamples are given in Example 5.

81. The method of clause 79, wherein the current video block is 4×8 or8×4, and determining includes determining that bi-prediction isdisallowed.

82. The method of clause 79, wherein the current video block is 4×N,where N is an integer<=16, and determining includes determining thatbi-prediction is disallowed.

83. The method of any of clauses 26-29 or 79-82, wherein the size of thecurrent block corresponds to on a size of a color component or a lumacomponent of the current block.

84. The method of clause 83, wherein the disabling bi-prediction oruni-prediction is applied to all three components of the current videoblock.

85. The method of clause 83, wherein the disabling bi-prediction oruni-prediction is applied only to a color component whose size is usedas the size of the current block.

86. The method of any of clauses 79 to 85, wherein the conversion isperformed by disabling bi-prediction and further using a merge candidatethat is bi-predicted, then assigning only one motion vector from onlyone reference list to the current video block.

87. The method of clause 79, wherein the current video block is 4×4, anddetermining includes determining that both bi-prediction anduni-prediction are disallowed.

88. The method of clause 87, wherein the current video block is coded asan intra-block.

89. The method of clause 87, wherein the current video block isrestricted to using integer pixel motion vectors.

Additional examples and embodiments for clauses 78-89 are described inExample 5.

90. A method of processing video, comprising:

-   -   determining, based on a size of a current video block, a video        coding condition for the current video block; and    -   performing, based on the video coding condition, a conversion        between the current video block and a bitstream representation        of the current video block.

91. The method of clause 90, wherein the video coding conditionspecifies selectively signaling a skip flag or an intra block codingflag in the bitstream representation.

92. The method of clause 90 or 91, wherein the video coding conditionspecifies selectively signaling a prediction mode for the current videoblock.

93. The method of any of clauses 90 to 92, wherein the video codingcondition specifies selectively signaling a triangle mode coding of thecurrent video block.

94. The method of any of clauses 90 to 93, wherein the video codingcondition specifies selectively signaling an inter prediction directionfor the current video block.

95. The method of any of clauses 90 to 94, wherein the video codingcondition specifies selectively modifying motion vectors or blockvectors used for intra block copy of the current video block.

96. The method of any of clauses 90-95, wherein the video condition isdependent on a height in pixels of the current video block.

97. The method of any of clauses 90-96, wherein the video condition isdependent on a width in pixels of the current video block.

98. The method of any of clauses 90-95, wherein the video condition isdependent on whether the current video block is square shaped.

Additional examples of clauses 90 to 98 are provided in Items 11 to 16listed in Section 4 of the present document.

99. A video encoder apparatus that comprises a processor configured toperform a method recited in one or more of clauses 1 to 98.

100. A video decoder apparatus that comprises a processor configured toperform a method recited in one or more of clauses 1 to 98.

101. A computer readable medium having code stored thereon, the code,when executed by a processor, causing the processor to implement amethod recited in any one or more of clauses 1 to 98.

FIG. 16 is a block diagram showing an example video processing system1600 in which various techniques disclosed herein may be implemented.Various implementations may include some or all of the components of thesystem 1600. The system 1600 may include input 1602 for receiving videocontent. The video content may be received in a raw or uncompressedformat, e.g., 8 or 10 bit multi-component pixel values, or may be in acompressed or encoded format. The input 1602 may represent a networkinterface, a peripheral bus interface, or a storage interface. Examplesof network interface include wired interfaces such as Ethernet, passiveoptical network (PON), etc. and wireless interfaces such as Wi-Fi orcellular interfaces.

The system 1600 may include a coding component 1604 that may implementthe various coding or encoding methods described in the presentdocument. The coding component 1604 may reduce the average bitrate ofvideo from the input 1602 to the output of the coding component 1604 toproduce a coded representation of the video. The coding techniques aretherefore sometimes called video compression or video transcodingtechniques. The output of the coding component 1604 may be eitherstored, or transmitted via a communication connected, as represented bythe component 1606. The stored or communicated bitstream (or coded)representation of the video received at the input 1602 may be used bythe component 1608 for generating pixel values or displayable video thatis sent to a display interface 1610. The process of generatinguser-viewable video from the bitstream representation is sometimescalled video decompression. Furthermore, while certain video processingoperations are referred to as “coding” operations or tools, it will beappreciated that the coding tools or operations are used at an encoderand corresponding decoding tools or operations that reverse the resultsof the coding will be performed by a decoder.

Examples of a peripheral bus interface or a display interface mayinclude universal serial bus (USB) or high definition multimediainterface (HDMI) or Displayport, and so on. Examples of storageinterfaces include SATA (serial advanced technology attachment), PCI,IDE interface, and the like. The techniques described in the presentdocument may be embodied in various electronic devices such as mobilephones, laptops, smartphones or other devices that are capable ofperforming digital data processing and/or video display.

FIG. 17 is a flowchart representation of a method 1700 for videoprocessing in accordance with the present disclosure. The method 1700includes, at operation 1702, determining, for a conversion between acurrent block of a video and a bitstream representation of the videousing an affine coding tool, that a first motion vector of a sub-blockof the current block and a second motion vector that is a representativemotion vector for the current block comply with a size constraint. Themethod 1700 also includes, at operation 1704, performing the conversionbased on the determining.

In some embodiments, the first motion vector of the sub-block isrepresented as (MVx, MVy) and the second motion vector is represented as(MV′x, MV′y). The size constraint indicates that MVx>=MV′x-DH0,MVx<=MV′x+DH1, MVy>=MV′y-DV0, and MVy<=MV′y+DV1, DH0, DH1, DV0 and DV1being positive numbers. In some embodiments, DH0=DH1. In someembodiments, DH0≠DH1. In some embodiments, DV0=DV1. In some embodiments,DV0≠DV0. In some embodiments, DH0=DV0. In some embodiments, DH0≠DV0. Insome embodiments, DH1=DV1. In some embodiments, DH1≠DV1.

In some embodiments, at least one of DH0, DH1, DV0, or DV1 is signaledin the bitstream representation in a video parameter set level, asequence parameter set level, a picture parameter set level, a sliceheader, a tile group header, a tile level, a coding tree unit level, acoding unit level, or a prediction unit level. In some embodiments, DH0,DH1, DV0, and DV1 are different for different profiles, levels, or tiersof the conversion. In some embodiments, wherein DH0, DH1, DV0, and DV1are based on a weight or a height of the current block. In someembodiments, DH0, DH1, DV0, and DV1 are based on a prediction mode ofthe current block, the prediction mode being a uni-prediction mode or abi-prediction mode. In some embodiments, DH0, DH1, DV0, and DV1 arebased on a position of the sub-block in the current block.

In some embodiments, the second motion vector comprises a control pointmotion vector of the current block. In some embodiments, the secondmotion vector comprises a motion vector for a second sub-block of thecurrent block. In some embodiments, the second sub-block comprises acenter sub-block of the current block. In some embodiments, the secondsub-block comprises a corner sub-block of the current block. In someembodiments, the second motion vector comprises a motion vector derivedfor a position inside or outside of the current block, the positioncoded using a same affine model as the current block. In someembodiments, the position comprises a center position of the currentblock.

In some embodiments, the first motion vector is adjusted to satisfy thesize constraint. In some embodiments, the bitstream is invalid in casethe first motion vector fails to satisfy the size constraint withrespect to the second motion vector. In some embodiments, the firstmotion vector and the second motion vector are represented according toa motion vector signaling precision in the bitstream representation. Insome embodiments, the first motion vector and the second motion vectorare represented according to a storage precision for storing motionvectors. In some embodiments, the first motion vector and the secondmotion vector are represented according to a precision that is differentfrom a motion vector signaling precision or a storage precision forstoring motion vectors.

FIG. 18 is a flowchart representation of a method 1800 for videoprocessing in accordance with the present disclosure. The method 1800includes, at operation 1802, determining, for a conversion between acurrent block of a video and a bitstream representation of the video, anaffine model that comprises six parameters. The affine model isinherited from affine coding information of a neighboring block of thecurrent block. The method 1800 includes, at operation 1804, performingthe conversion based on the affine model.

In some embodiments, the neighboring block is coded using a secondaffine model having six parameters, the affine model being same as thesecond affine model. In some embodiments, the neighboring block is codedusing a third affine model having four parameters. In some embodiments,the affine model is determined based on a position of the current block.In some embodiments, the affine model is determined according to thethird affine model in case the neighboring block is not in a same codingtree unit (CTU) as the current block. In some embodiments, the affinemodel is determined according to the third affine model in case theneighboring block is not in a same CTU line or a same CTU row as thecurrent block.

In some embodiments, a tile, a slice, or a picture is split intomultiple non-overlapped regions. In some embodiments, the affine modelis determined according to the third affine model in case theneighboring block is not in a same region as the current block. In someembodiments, the affine model is determined according to the thirdaffine model in case the neighboring block is not in a same region lineor a same region row as the current block. In some embodiments, eachregion has a size of 64×64. In some embodiments, a top-left corner ofthe current block is represented as (x, y) and a top-left corner of theneighboring block is represented as (x′, y′), and wherein the affinemodel is determined according to the third affine model in case acondition regarding x, y, x′ and y′ is satisfied. In some embodiments,the condition indicates x/M≠x′/M, M being a positive integer. In someembodiments, M is 128 or 64. In some embodiments, the conditionindicates y/N≠y′/N, N being a positive integer. In some embodiments, Nis 128 or 64. In some embodiments, the condition indicates x/M≠x′/M andy/N≠y′/N, M and N being a positive integer. In some embodiments, M=N=128or M=N=64. In some embodiments, the condition indicates x>>M≠x′>>M, Mbeing a positive integer. In some embodiments, M is 6 or 7. In someembodiments, the condition indicates y>>N≠y′>>N, N being a positiveinteger. In some embodiments, N is 6 or 7. In some embodiments, thecondition indicates x>>M≠x′>>M and y>>N≠y′>>N, M and N being a positiveinteger. In some embodiments, M=N=6 or M=N=7.

FIG. 19 is a flowchart representation of a method 1900 for videoprocessing in accordance with the present disclosure. The method 1900includes, at operation 1902, determining, for a conversion between ablock of a video and a bitstream representation of the video, whether abi-prediction coding technique is applicable to the block based on asize of the block having a width W and a height H, W and H beingpositive integers. The method 1900 includes, at operation 1904,performing the conversion according to the determining.

In some embodiments, the bi-prediction coding technique is notapplicable in case W=T1 and H=T2, T1 and T2 being positive integers. Insome embodiments, the bi-prediction coding technique is not applicablein case W=T2 and H=T1, T1 and T2 being positive integers. In someembodiments, the bi-prediction coding technique is not applicable incase W=T1 and H≤T2, T1 and T2 being positive integers. In someembodiments, the bi-prediction coding technique is not applicable incase W≤T2 and H=T1, T1 and T2 being positive integers. In someembodiments, T1=4 and T2=16. In some embodiments, the bi-predictioncoding technique is not applicable in case W≤T1 and H≤1 T2, T1 and T2being positive integers. In some embodiments, T1=T2=8. In someembodiments, T1=8 and T2=4. In some embodiments, T1=T2=4. In someembodiments, T1=4 and T2=8.

In some embodiments, an indicator indicating information about thebi-prediction coding technique is signaled in the bitstream in case thebi-prediction coding technique is applicable. In some embodiments, anindicator indicating information about the bi-prediction codingtechnique for the block is excluded from the bitstream in case thebi-prediction coding technique is not applicable to the block. In someembodiments, the bi-prediction coding technique is not applicable incase the size of the block is one of: 4×8 or 8×4. In some embodiments,the bi-prediction coding technique is not applicable in case the size ofthe block is 4×N or N×4, N being a positive integer and N≤16. In someembodiments, the size of the block corresponds to a first colorcomponent of the block, and whether a bi-prediction coding technique isapplicable is determined for the first color component and remainingcolor components of the block. In some embodiments, the size of theblock corresponds to a first color component of the block, and whether abi-prediction coding technique is applicable is determined only for thefirst color component. In some embodiments, the first color componentincludes a luma component.

In some embodiments, the method further comprises, in case thebi-prediction coding technique is not applicable to the current block,assigning a single motion vector from a first reference list or a secondreference list upon determining that a selected merge candidate is codedusing the bi-prediction coding technique. In some embodiments, themethod further comprises, in case the bi-prediction coding technique isnot applicable to the current block, determining that a triangularprediction mode is not applicable to the block. In some embodiments,whether the bi-prediction coding technique is applicable is associatedwith a prediction direction, the prediction direction further associatedwith a uni-prediction coding technique, and wherein the predictiondirection is signaled in the bitstream based on the size of the block.In some embodiments, information about the uni-prediction codingtechnique is signaled in the bitstream in case (1) W×H<64 or (2) W×H=64,W being unequal to H. In some embodiments, information about theuni-prediction coding technique or the bi-direction coding technique issignaled in the bitstream in case (1) W×H>64 or (2) W×H=64, W beingequal to H.

In some embodiments, a restriction indicates that neither thebi-direction coding technique nor the uni-direction technique isapplicable to the block in case the size of the block is 4×4. In someembodiments, the restriction is applicable in case the block is affinecoded. In some embodiments, the restriction is applicable in case theblock is not affine coded. In some embodiments, the restriction isapplicable in case the block is intra-coded. In some embodiments, therestriction is not applicable in case a motion vector of the block hasan integer precision.

In some embodiments, signaling that the block is generated based on asplit of a parent block is skipped in the bitstream, the parent blockhaving a size of (1) 8×8 for a quad-tree split, (2) 8×4 or 4×8 for abinary tree split, (3) or 4×16 or 16×4 for a triple tree split. In someembodiments, an indicator indicating that the motion vector has theinteger precision is set to 1 in the bitstream. In some embodiments, themotion vector of the block is rounded to the integer precision.

In some embodiments, the bi-prediction coding technique is applicable tothe block. A reference block has a size of (W+N−1−PW)×(H+N−1−PH), andboundary pixels of the reference block are repeated to generate a secondblock having a size of (W+N−1)×(H+N−1) for an interpolation operation, Nrepresenting an interpolation filter tap, N, PW and PH being integers.In some embodiments, PH=0, and pixels of at least a left boundary or aright boundary are repeated to generate the second block. In someembodiments, PW=0, and pixels of at least a top boundary or a bottomboundary are repeated to generate the second block. In some embodiments,PW>0 and PH>0, and the second block is generated by repeating pixels ofat least a left boundary or a right boundary followed by repeatingpixels of at least a top boundary or a bottom boundary. In someembodiments, PW>0 and PH>0, and the second block is generated byrepeating pixels of at least a top boundary or a bottom boundaryfollowed by repeating pixels of at least a left boundary or a rightboundary. In some embodiments, pixels of a left boundary are repeated M1times, and wherein pixels of a right boundary are repeated (PW−M1)times. In some embodiments, pixels of a top boundary are repeated M2times, and wherein pixels of a bottom boundary are repeated (PH−M2)times. In some embodiments, how the boundary pixels of the referenceblock are repeated is applied to some or all reference blocks for theconversion. In some embodiments, PW and PH are different for differentcomponents of the block.

In some embodiments, a merge candidate list construction process isperformed based on the size of the block. In some embodiments, a mergecandidate is considered as a uni-prediction candidate referring to afirst reference list in a uni-prediction coding technique in case (1)the merge candidate is coded using the bi-prediction coding techniqueand (2) bi-prediction is not applicable to the block according to thesize of the block. In some embodiments, the first reference listcomprises a reference list 0 or a reference list 1 of the uni-predictioncoding technique. In some embodiments, a merge candidate is consideredas unavailable in case (1) the merge candidate is coded using thebi-prediction coding technique and (2) bi-prediction is not applicableto the block according to the size of the block. In some embodiments,the unavailable merge candidate is removed from a merge candidate listin the merge candidate list construction process. In some embodiments,the merge candidate list construction process for Triangular PredictionMode is invoked in case bi-prediction is not applicable to the blockaccording to the size of the block.

FIG. 20 is a flowchart representation of a method 2000 for videoprocessing in accordance with the present disclosure. The method 2000includes, at operation 2002, determining, for a conversion between ablock of a video and a bitstream representation of the video, whether acoding tree split process is applicable to the block based on a size ofa sub-block that is a child coding unit of the block according to thecoding tree split process. The sub-block has a width W and a height H, Wand H being positive integers. The method 2000 also includes, atoperation 2004, performing the conversion according to the determining.

In some embodiments, the coding tree split process is not applicable incase W=T1 and H=T2, T1 and T2 being positive integers. In someembodiments, the coding tree split process is not applicable in caseW=T2 and H=T1, T1 and T2 being positive integers. In some embodiments,the coding tree split process is not applicable in case W=T1 and H≤T2,T1 and T2 being positive integers. In some embodiments, the coding treesplit process is not applicable in case W≤T2 and H=T1, T1 and T2 beingpositive integers. In some embodiments, T1=4 and T2=16. In someembodiments, the coding tree split process is not applicable in caseW≤T1 and H≤T2, T1 and T2 being positive integers. In some embodiments,T1=T2=8. In some embodiments, T1=8 and T2=4. In some embodiments,T1=T2=4. In some embodiments, T1=4. In some embodiments, T2=4. In someembodiments, signaling of the coding tree split process is omitted fromthe bitstream in case the coding tree split process is not applicable tothe current block.

FIG. 21 is a flowchart representation of a method 2100 for videoprocessing in accordance with the present disclosure. The method 2100includes, at operation 2102, determining, for a conversion between acurrent block of a video and a bitstream representation of the video,whether an index of a bi-prediction with coding unit level weight (BCW)coding mode is derived based on a rule with respect to a position of thecurrent block. In the BCW coding mode, a weight set including multipleweights is used to generate bi-prediction values of the current block.The method 2100 also includes, at operation 2104, performing theconversion based on the determining.

In some embodiments, the bi-prediction values of the current block aregenerated as a non-averaging weighted sum of two motion vectors in caseat least one weight in the weight set is applied. In some embodiments,rule specifies that the index is not derived according to theneighboring block in case the current block and the neighboring blockare positioned in different coding tree units or largest coding units.In some embodiments, the rule specifies the index is not derivedaccording to the neighboring block in case the current block and theneighboring block are positioned in different lines or rows in a codingtree unit. In some embodiments, the rule specifies the index is notderived according to the neighboring block in case the current block andthe neighboring block are positioned in different non-overlapped regionsof a tile, a slice, or a picture of the video. In some embodiments, therule specifies the index is not derived according to the neighboringblock in case the current block and the neighboring block are positionedin different rows of non-overlapped regions of a tile, a slice, or apicture of the video. In some embodiments, each region has a size of64×64.

In some embodiments, a top corner of the current block is represented as(x,y) and a top corner of the neighboring block is represented as (x′,y′). The rule specifies the index is not derived according to theneighboring block in case (x, y) and (x′, y′) satisfy a condition. Insome embodiments, the condition indicates that x/M≠x′/M, M being apositive integer. In some embodiments, M is 128 or 64. In someembodiments, the condition indicates that y/N≠y′/N, N being a positiveinteger. In some embodiments, N is 128 or 64. In some embodiments, thecondition indicates that (x/M≠x′/M) and (y/N≠y′/N), M and N beingpositive integers. In some embodiments, M=N=128 or M=N=64. In someembodiments, the condition indicates that x>>M≠x′>>M, M being a positiveinteger. In some embodiments, M is 6 or 7. In some embodiments, thecondition indicates that y>>N≠y′>>N, N being a positive integer. In someembodiments, wherein N is 6 or 7. In some embodiments, the conditionindicates that (x>>M≠x′>>M) and (y>>N≠y′>>N), M and N being positiveintegers. In some embodiments, M=N=6 or M=N=7.

In some embodiments, whether the BCW coding mode is applicable to apicture, a slice, a tile group, or a tile is signaled respectively in apicture parameter set, a slice header, a tile group header, or a tile inthe bitstream. In some embodiments, whether the BCW coding mode isapplicable to a picture, a slice, a tile group, or a tile is derivedbased on information associated with the picture, the slice, the tilegroup, or the tile. In some embodiments, the information comprises atleast a quantization parameter (QP), a temporal layer, or a PictureOrder Count distance.

FIG. 22 is a flowchart representation of a method 2200 for videoprocessing in accordance with the present disclosure. The method 2200includes, at operation 2202, determining, for a conversion between acurrent block of a video coded using a combined inter and intraprediction (CIIP) coding technique and a bitstream representation of thevideo, an intra-prediction mode of the current block independently froman intra-prediction mode of a neighboring block. The CIIP codingtechnique uses an intermediate inter prediction value and anintermediate intra prediction value to derive a final prediction valueof the current block. The method 2200 also includes, at operation 2204,performing the conversion based on the determining.

In some embodiments, the intra-prediction mode of the current block isdetermined without referencing an intra-prediction prediction mode ofany neighboring blocks. In some embodiments, a neighboring block iscoded using the CIIP coding technique. In some embodiments, theintra-prediction of the current block is determined based on anintra-prediction mode of a second neighboring block that is coded usingan intra-prediction coding technique. In some embodiments, whether todetermine the intra-prediction mode of the current block according tothe second intra-prediction mode is based on whether a condition issatisfied, the condition specifying a relationship between the currentblock as a first block and the second neighboring block as a secondblock. In some embodiments, the determining is a part of a Most ProbableModes (MPM) construction process of the current block to derive a listof MPM modes.

FIG. 23 is a flowchart representation of a method 2300 for videoprocessing in accordance with the present disclosure. The method 2300includes, at operation 2302, determining, for a conversion between acurrent block of a video coded using a combined inter and intraprediction (CIIP) coding technique and a bitstream representation of thevideo, an intra-prediction mode of the current block according to afirst intra-prediction mode of a first neighboring block and a secondintra-prediction mode of a second neighboring block. The firstneighboring block is coded using an intra-prediction coding techniqueand the second neighboring block is coded using the CIIP codingtechnique. The first intra-prediction mode is given a priority differentthan the second intra-prediction mode. The CIIP coding technique uses anintermediate inter prediction value and an intermediate intra predictionvalue to derive a final prediction value of the current block. Themethod 2300 also includes, at operation 2304, performing the conversionbased on the determining.

In some embodiments, the determining is a part of a Most Probable Modes(MPM) construction process of the current block to derive a list of MPMmodes. In some embodiments, the first intra-prediction mode ispositioned prior to the second intra-prediction mode in the list of MPMcandidates. In some embodiments, the first intra-prediction mode ispositioned after the second intra-prediction mode in the list of MPMcandidates. In some embodiments, coding of the intra-prediction modebypasses a Most Probable Modes (MPM) construction process of the currentblock. In some embodiments, the method also comprises determining anintra-prediction mode of a subsequent block according to theintra-prediction mode of the current block, wherein the subsequent blockis coded using an intra-prediction coding technique and the currentblock is coded using the CIIP coding technique. In some embodiments, thedetermining is a part of a Most Probable Modes (MPM) constructionprocess of the subsequent block. In some embodiments, in the MPMconstruction process of the subsequent block, the intra-prediction modeof the current block is given a lower priority than an intra-predictionmode of another neighboring block coded using the intra-predictioncoding technique. In some embodiments, whether to determine theintra-prediction mode of the subsequent block according to theintra-prediction mode of the current block is based on whether acondition is satisfied, the condition specifying a relationship betweenthe subsequent block as a first block and the current block as a secondblock. In some embodiments, the condition comprises at least one of: (1)the first block and the second block are positioned in a same line of acoding tree unit (CTU), (2) the first block and the second block arepositioned in the same CTU, (3) the first block and the second block arein a same region, or (4) the first block and the second block are in asame line of the region. In some embodiments, a width of the region issame as a height of the region. In some embodiments, the region has asize of 64×64.

In some embodiments, only a subset of a list of Most Probable Modes(MPMs) for a normal intra coding technique is used for the currentblock. In some embodiments, the subset comprises a single MPM mode inthe list of MPM modes for the normal intra coding technique. In someembodiments, the single MPM mode is a first MPM mode in the list. Insome embodiments, an index indicating the single MPM mode is omitted inthe bitstream. In some embodiments, the subset comprises first four MPMmodes in the list of MPM modes. In some embodiments, an index indicatingan MPM mode in the subset is signaled in the bitstream. In someembodiments, a coding context for coding the intra-coded block is reusedfor coding the current block. In some embodiments, a first MPM flag forthe intra-coded block and a second MPM flag for the current block sharethe same coding context in the bitstream. In some embodiments, theintra-prediction mode of the current block is selected from the list ofMPM modes regardless of a size of the current block. In someembodiments, the MPM construction processed is defaulted to be enabled,and wherein a flag indicating the MPM construction process is omitted inthe bitstream. In some embodiments, no MPM list construction process isneeded for the current block.

In some embodiments, a luma-predict-chroma mode is used for processing achroma component of the current block. In some embodiments, a derivedmode is used for processing the chroma component of the current block.In some embodiments, multiple intra-prediction modes are used forprocessing the chroma component of the current block. In someembodiments, the multiple intra-prediction modes are used based on acolor format of the chroma component. In some embodiments, in case thecolor format is 4:4:4, the multiple intra-prediction modes are same asintra-prediction modes for a luma component of the current block. Insome embodiments, each of four intra-prediction modes is coded using oneor more bits, the four intra-prediction modes including a Planar mode, aDC mode, a Vertical mode, and a Horizontal mode. In some embodiments,the four intra-prediction modes are coded using 00, 01, 10, and 11. Insome embodiments, the four intra-prediction modes are coded using 0, 10,110, 111. In some embodiments, the four intra-prediction modes are codedusing 1, 01, 001, 000. In some embodiments, in case a width W and aheight H of the current block satisfy a condition, only a subset of thefour intra-prediction modes is available for use. In some embodiments,the subset comprises the Planar mode, the DC mode, and the Vertical modein case W>N×H, N being an integer. In some embodiments, the Planar mode,the DC mode, and the Vertical mode are coded using 1, 01, and 11. Insome embodiments, the Planar mode, the DC mode, and the Vertical modeare coded using 0, 10, and 00. In some embodiments, the subset comprisesthe Planar mode, the DC mode, and the Horizontal mode in case H>N×W, Nbeing an integer. In some embodiments, the Planar mode, the DC mode, andthe Horizontal mode are coded using 1, 01, and 11. In some embodiments,the Planar mode, the DC mode, and the Horizontal mode are coded using 0,10, and 00. In some embodiments, N=2. In some embodiments, only a DCmode and a Planar mode are used for the current block. In someembodiments, an indicator indicating the DC mode or the Planar mode issignaled in the bitstream.

FIG. 24 is a flowchart representation of a method 2400 for videoprocessing in accordance with the present disclosure. The method 2400includes, at operation 2402, determining, for a conversion between acurrent block of a video and a bitstream representation of the video,whether a combined inter intra prediction (CIIP) process is applicableto a color component of the current block based on a size of the currentblock. The CIIP coding technique uses an intermediate inter predictionvalue and an intermediate intra prediction value to derive a finalprediction value of the current block. The method 2400 also includes, atoperation 2404, performing the conversion based on the determining.

In some embodiments, the color component comprises a chroma component,and wherein the CIIP process is not performed to the chroma component incase a width of the current block is smaller than 4. In someembodiments, the color component comprises a chroma component, andwherein the CIIP process is not performed to the chroma component incase a height of the current block is smaller than 4. In someembodiments, an intra-prediction mode for a chroma component of thecurrent block is different than an intra-prediction mode for a lumacomponent of the current block. In some embodiments, the chromacomponent uses one of: a DC mode, a Planar mode, or aLuma-predict-chroma mode. In some embodiments, the intra-prediction modefor the chroma component is determined based on color format of thechroma component. In some embodiments, the color format comprises 4:2:0or 4:4:4.

FIG. 25 is a flowchart representation of a method 2500 for videoprocessing in accordance with the present disclosure. The method 2500includes, at operation 2502, determining, for a conversion between acurrent block of a video and a bitstream representation of the video,whether a combined inter and intra prediction (CIIP) coding technique isto be applied to the current block based on a characteristic of thecurrent block. The CIIP coding technique uses an intermediate interprediction value and an intermediate intra prediction value to derive afinal prediction value of the current block. The method 2500 alsoincludes, at operation 2504, performing the conversion based on thedetermining.

In some embodiments, the characteristic comprises a size of the currentblock having a width W and a height H, W and H being integers, and theinter-intra prediction coding technique is disabled for the currentblock in case the size of the block satisfies a condition. In someembodiments, the condition indicates that W is equal to T1, T1 being aninteger. In some embodiments, the condition indicates that H is equal toT1, T1 being an integer. In some embodiments, T1=4. In some embodiments,T1=2. In some embodiments, the condition indicates that W is greaterthan T1 or H is greater than T1, T1 being an integer. In someembodiments, T1=64 or 128. In some embodiments, the condition indicatesthat W is equal to T1 and H is equal to T2, T1 and T2 being integers. Insome embodiments, the condition indicates that W is equal to T2 and H isequal to T1, T1 and T2 being integers. In some embodiments, T1=4 andT2=16.

In some embodiments, the characteristic comprises a coding techniqueapplied to the current block, and the CIIP coding technique is disabledfor the current block in case the coding technique satisfies acondition. In some embodiments, the condition indicates that the codingtechnique is a bi-prediction coding technique. In some embodiments, abi-prediction coded merge candidate is converted to a uni-predictioncoded merge candidate to allow the inter-intra prediction codingtechnique to be applied to the current block. In some embodiments, theconverted merge candidate is associated with a referent list 0 of auni-prediction coding technique. In some embodiments, the convertedmerge candidate is associated with a referent list 1 of a uni-predictioncoding technique. In some embodiments, only uni-prediction coded mergecandidates of the block are selected for the conversion. In someembodiments, bi-prediction coded merge candidates are discarded fordetermining a merge index indicating a merge candidate in the bitstreamrepresentation. In some embodiments, the inter-intra prediction codingtechnique is applied to the current block according to the determining.In some embodiments, a merge candidate list construction process for aTriangular Prediction Mode is used to derive a motion candidate list forthe current block.

FIG. 26 is a flowchart representation of a method 2600 for videoprocessing in accordance with the present disclosure. The method 2600includes, at operation 2602, determining, for a conversion between acurrent block of a video and a bitstream representation of the video,whether a coding tool is to be disabled for the current block based onwhether the current block is coded with a combined inter and intraprediction (CIIP) coding technique. The CIIP coding technique uses anintermediate inter prediction value and an intermediate intra predictionvalue to derive a final prediction value of the current block. Thecoding tool comprises at least one of: a Bi-Directional Optical Flow(BDOF), an Overlapped Block Motion Compensation (OBMC), or adecoder-side motion vector refinement process (DMVR). The method 2500also includes, at operation 2604, performing the conversion based on thedetermining.

In some embodiments, an intra-prediction process for the current blockis different from an intra-prediction process for a second block that iscoded using an intra-prediction coding technique. In some embodiments,in the intra-prediction process for the current block, filtering ofneighboring samples is skipped. In some embodiments, in theintra-prediction process for the current block, a position-dependentintra prediction sample filtering process is disabled. In someembodiments, in the intra-prediction process for the current block, amultiline intra-prediction process is disabled. In some embodiments, inthe intra-prediction process for the current block, a wide-angleintra-prediction process is disabled.

FIG. 27 is a flowchart representation of a method 2700 for videoprocessing in accordance with the present disclosure. The method 2700includes, at operation 2702, determining, for a conversion between ablock of a video and a bitstream representation of the video, a firstprecision P1 used for motion vectors for spatial motion prediction and asecond precision P2 used for motion vectors for temporal motionprediction. P1 and/or P2 are fractions. P1 and P2 are different fromeach other. The method 2600 also includes, at operation 2704, performingthe conversion based on the determining.

In some embodiments, the first precision is 1/16 luma pixel and thesecond precision is ¼ luma pixel. In some embodiments, the firstprecision is 1/16 luma pixel and the second precision is ⅛ luma pixel.In some embodiments, the first precision is ⅛ luma pixel and the secondprecision is ¼ luma pixel. In some embodiments, the first precision is1/16 luma pixel and the second precision is ¼ luma pixel. In someembodiments, the first precision is 1/16 luma pixel and the secondprecision is ⅛ luma pixel. In some embodiments, the first precision is ⅛luma pixel and the second precision is ¼ luma pixel. In someembodiments, at least one of the first or second precision is lower than1/16 luma pixel.

In some embodiments, at least one of the first or the second precisionis variable. In some embodiments, the first precision or the secondprecision is variable according to a profile, a level, or a tier of thevideo. In some embodiments, the first precision or the second precisionis variable according to a temporal layer of a picture in the video. Insome embodiments, the first precision or the second precision isvariable according to a size of a picture in the video.

In some embodiments, at least one of the first or the second precisionis signaled in a video parameter set, a sequence parameter set, apicture parameter set, a slice header, a tile group header, a tile, acoding tree unit, or a coding unit in the bitstream representation. Insome embodiments, a motion vector is represented as (MVx, MVy) and aprecision for the motion vector is represented as (Px, Py), and whereinPx is associated with MVx and Py is associated with MVy. In someembodiments, Px and Py are variables according to a profile, a level, ora tier of the video. In some embodiments, Px and Py are variableaccording to a temporal layer of a picture in the video. In someembodiments, Px and Py are variables according to a width of a picturein the video. In some embodiments, Px and Py are signaled in a videoparameter set, a sequence parameter set, a picture parameter set, aslice header, a tile group header, a tile, a coding tree unit, or acoding unit in the bitstream representation. In some embodiments, adecoded motion vector is denoted as (MVx, MVy), and wherein the motionvector is adjusted according to the second precision prior to the motionvector is stored as a temporal motion prediction motion vector. In someembodiments, temporal motion prediction motion vector is adjusted to be(Shift(MVx, P1-P2), Shift(MVy, P1-P2)), P1 and P2 being integers andP1≥P2, Shift representing a right shift operation on an unsigned number.In some embodiments, the temporal motion prediction motion vector isadjusted to be (SignShift(MVx, P1-P2), SignShift(MVy, P1-P2)), P1 and P2being integers and P1≥P2, SignShift representing a right shift operationon a signed number. In some embodiments, the temporal motion predictionmotion vector is adjusted to be (MVx<<(P1-P2)), MVy<<(P1-P2)), P1 and P2being integers and P1≥P2, <<representing a left shift operation on asigned or an unsigned number.

FIG. 28 is a flowchart representation of a method 2800 for videoprocessing in accordance with the present disclosure. The method 2800includes, at operation 2802, determining, for a conversion between ablock of a video and a bitstream representation of the video, a motionvector (MVx, MVy) with a precision (Px, Py). Px is associated with MVxand Py is associated with MVy. MVx and MVy are represented using N bits,and MinX≤MVx≤MaxX and MinY≤MVy≤MaxY, MinX, MaxX, MinY, and MaxY beingreal numbers. The method 2700 also includes, at operation 2804,performing the conversion based on the determining.

In some embodiments, MinX=MinY. In some embodiments, MinX≠MinY. In someembodiments, MaxX=MaxY. In some embodiments, MaxX≠MaxY.

In some embodiments, at least one of MinX or MaxX is based on Px. Insome embodiments, the motion vector has a precision denoted as (Px, Py),and wherein at least one of MinY or MaxY is based on Py. In someembodiments, at least one of MinX, MaxX, MinY, or MaxY is based on N. Insome embodiments, at least one of MinX, MaxX, MinY, or MaxY for aspatial motion prediction motion vector is different than acorresponding MinX, MaxX, MinY, or MaxY for a temporal motion predictionmotion vector. In some embodiments, at least one of MinX, MaxX, MinY, orMaxY is variable according to a profile, a level, or a tier of thevideo. In some embodiments, at least one of MinX, MaxX, MinY, or MaxY isvariable according to a temporal layer of a picture in the video. Insome embodiments, at least one of MinX, MaxX, MinY, or MaxY is variableaccording to a size of a picture in the video. In some embodiments, atleast one of MinX, MaxX, MinY, or MaxY is signaled in a video parameterset, a sequence parameter set, a picture parameter set, a slice header,a tile group header, a tile, a coding tree unit, or a coding unit in thebitstream representation. In some embodiments, MVx is clipped to [MinX,MaxX] before being used for spatial motion prediction or temporal motionprediction. In some embodiments, MVy is clipped to [MinY, MaxY] beforebeing used for spatial motion prediction or temporal motion prediction.

FIG. 29 is a flowchart representation of a method 2900 for videoprocessing in accordance with the present disclosure. The method 2900includes, at operation 2902, determining, for a conversion between acurrent block of a video and a bitstream representation of the video,whether a shared merge list is applicable to the current block accordingto a coding mode of the current block. The method 2800 includes, atoperation 2904, performing the conversion based on the determining.

In some embodiments, the shared merge list is not applicable in case thecurrent block is coded using a regular merge mode. In some embodiments,the shared merge list is applicable in case the current block is codedusing an Intra Block Copy (IBC) mode. In some embodiments, the methodfurther comprises: maintaining, prior to performing the conversion, atable of motion candidates based on past conversions of the video andthe bitstream representation; and disabling, after performing theconversion, an update of the table of motion candidates in case thecurrent block is a child of a parent block to which a shared merge listis applicable, and the current block is coded using a regular mergemode.

FIG. 30 is a flowchart representation of a method 3000 for videoprocessing in accordance with the present disclosure. The method 3000includes, at operation 3002, determining, for a conversion between acurrent block of video having a W×H size and a bitstream representationof the video, a second block of a dimension (W+N−1)×(H+N−1) for motioncompensation during the conversion. The second block is determined basedon a reference block of a dimension (W+N−1−PW)×(H+N−1−PH). N representsa filter size, and W, H, N, PW and PH are non-negative integers. PW andPH are not both equal to 0. The method 3000 also includes, at operation3004, performing the conversion based on the determining.

In some embodiments, pixels in the second block that are located outsideof the reference block are determined by repeating one or moreboundaries of the reference block. In some embodiments, PH=0, and atleast a left boundary or a right boundary of the reference block isrepeated to generate the second block. In some embodiments, PW=0, and atleast a top boundary or a bottom boundary of the reference block isrepeated to generate the second block. In some embodiments, PW>0 andPH>0, and the second block is generated by repeating at least a leftboundary or a right boundary of the reference block and subsequentlyrepeating at least a top boundary or a bottom boundary of the referenceblock. In some embodiments, PW>0 and PH>0, and the second block isgenerated by repeating at least a top boundary or a bottom boundary ofthe reference block and subsequently repeating at least a left boundaryor a right boundary of the reference block.

In some embodiments, a left boundary of the reference block is repeatedM1 times, and a right boundary of the reference block is repeated(PW−M1) times, M1 being a positive integer. In some embodiments, a topboundary of the reference block is repeated M2 times, and a bottomboundary of the reference block is repeated (PH−M2) times, M2 being apositive integer. In some embodiments, at least one of PW or PH isdifferent for different color components of the current block, the colorcomponents including at least a luma component or one or more chromacomponents. In some embodiments, at least one of PW or PH is variableaccording to a size or a shape of the current block. In someembodiments, at least one of PW or PH is variable according to a codingcharacteristic of the current block, the coding characteristic includinguni-prediction coding or a bi-prediction coding.

In some embodiments, pixels in the second block that are located outsideof the reference block are set to a single value. In some embodiments,the single value is 1<<(BD−1), BD being a bit-depth of pixel samples inthe reference block. In some embodiments, BD is 8 or 10. In someembodiments, the single value is derived based on pixel samples of thereference block. In some embodiments, the single value is signaled in avideo parameter set, a sequence parameter set, a picture parameter set,a slice header, a tile group header, a tile, a coding tree unit row, acoding tree unit, a coding unit, or a prediction unit. In someembodiments, padding of pixels in the second block that are locatedoutside of the reference block is disabled in case the current block isaffine coded.

FIG. 31 is a flowchart representation of a method 3000 for videoprocessing in accordance with the present disclosure. The method 3000includes, at operation 3102, determining, for a conversion between acurrent block of a video having a W×H size and a bitstreamrepresentation of the video, a second block of a dimension(W+N−1)×(H+N−1) for motion compensation during the conversion. W, H arenon-negative integers, and wherein N are non-negative integers and basedon a filter size. During the conversion, a refined motion vector isdetermined based on a multi-point search according to a motion vectorrefinement operation on an original motion vector, and wherein pixelslong boundaries of the reference block are determined by repeating oneor more non-boundary pixels. The method 3100 also includes, at operation3104, performing the conversion based on the determining,

In some embodiments, processing the current block comprises filteringthe current block in a motion vector refinement operation. In someembodiments, whether the reference block is applicable to the processingof the current block is determined based on a dimension of the currentblock. In some embodiments, interpolating the current block comprises:interpolating multiple sub-blocks of the current block based on thesecond block. Each sub-block has a size of W1×H1, W1, H1 beingnon-negative integers. In some embodiments, W1=H1=4, W=H=8, and PW=PH=0.In some embodiments, the second block is determined entirely based on aninteger part of a motion vector of at least one of the multiplesub-blocks. In some embodiments, in case a maximum difference betweeninteger parts of motion vectors of all the multiple sub-blocks is equalto or less than 1 pixel, the reference block is determined based on aninteger part of a motion vector of a top-left sub-block of the currentblock, and each of the right boundary and the bottom boundary of thereference block is repeated once to obtain the second block. In someembodiments, in case a maximum difference between integer parts ofmotion vectors of all the multiple sub-blocks is equal to or less than 1pixel, the reference block is determined based on an integer part of amotion vector of a bottom-right sub-block of the current block, and eachof the left boundary and the top boundary of the reference block isrepeated once to obtain the second block. In some embodiments, thesecond block is determined entirely based on a modified motion vector ofone of the multiple sub-blocks.

In some embodiments, in case a maximum difference between integer partsof motion vectors of all the multiple sub-blocks is equal to or lessthan two pixels, a motion vector of a top-left sub-block of the currentblock is modified by adding one integer pixel distance to each componentto obtain the modified motion vector. The reference block is determinedbased on the modified motion vector, and each of the left boundary, theright boundary, the top boundary, and the bottom boundary of thereference block is repeated once to obtain the second block.

In some embodiments, in case a maximum difference between integer partsof motion vectors of all the multiple sub-blocks is equal to or lessthan two pixels, a motion vector of a bottom-right sub-block of thecurrent block is modified by subtracting one integer pixel distance fromeach component to obtain the modified motion vector. The reference blockis determined based on the modified motion vector, and each of the leftboundary, the right boundary, the top boundary, and the bottom boundaryof the reference block is repeated once to obtain the second block.

FIG. 32 is a flowchart representation of a method 3200 for videoprocessing in accordance with the present disclosure. The method 3200includes, at operation 3202, determining, for a conversion of a block ofa video that is coded using a Combined Inter and Intra Prediction (CIIP)coding technique and a bitstream representation of the video, aprediction value at a position in the block based on a weighted sum ofan inter prediction value and an intra prediction value at the position.The weighted sum is based on adding an offset to an initial sum obtainedbased on the inter prediction value and the intra prediction value, andthe offset is added prior to a right-shift operation performed todetermine the weighted sum. The method 3200 also includes, at operation3204, performing the conversion based on the determining.

In some embodiments, the position in the block is represented as (x, y),the inter prediction value at the position (x, y) is represented asPinter(x, y), the intra prediction value at the position (x, y) isrepresented as Pintra(x, y), an inter-prediction weight at the position(x, y) is represented as w_inter(x, y), and an intra-prediction weightat the position (x, y) is represented as w_intra(x, y). The predictionvalue at the position (x, y) is determined to be (Pintra(x,y)×w_intra(x, y)+Pinter(x, y)×w_inter(x, y)+offset(x, y))>>N, whereinw_intra(x, y)+w_inter(x, y)=2{circumflex over ( )}N and offset(x,y)=2{circumflex over ( )}(N−1), N being a positive integer. In someembodiments, N=2.

In some embodiments, the weighted sum is determined using equal weightsfor the inter prediction value and the intra prediction value at theposition. In some embodiments, a zero weight is used according to theposition in the block to determine the weighted sum. In someembodiments, the zero weight is applied to the inter prediction value.In some embodiments, the zero weight is applied to the intra predictionvalue.

In some embodiments, performing the conversion in the above methodsincludes generating the bitstream representation based on the currentblock of the video. In some embodiments, performing the conversion inthe above methods includes generating the current block of the videofrom the bitstream representation.

The disclosed and other solutions, examples, embodiments, modules andthe functional operations described in this document can be implementedin digital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this document and theirstructural equivalents, or in combinations of one or more of them. Thedisclosed and other embodiments can be implemented as one or morecomputer program products, e.g., one or more modules of computer programinstructions encoded on a computer readable medium for execution by, orto control the operation of, data processing apparatus. The computerreadable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter effecting a machine-readable propagated signal, or a combinationof one or more them. The term “data processing apparatus” encompassesall apparatus, devices, and machines for processing data, including byway of example a programmable processor, a computer, or multipleprocessors or computers. The apparatus can include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, or acombination of one or more of them. A propagated signal is anartificially generated signal, e.g., a machine-generated electrical,optical, or electromagnetic signal, that is generated to encodeinformation for transmission to suitable receiver apparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random-access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non-volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any subject matter or of whatmay be claimed, but rather as descriptions of features that may bespecific to particular embodiments of particular techniques. Certainfeatures that are described in this patent document in the context ofseparate embodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

The invention claimed is:
 1. A method for video processing, comprising:determining, for a conversion between a current block of a video codedusing a combined inter and intra prediction coding technique and abitstream of the video, an intra-prediction mode of the current blockindependently from an intra-prediction mode of a neighboring block; andperforming the conversion based on the determining; wherein a weightpair is determined for the current block, and the weight pair comprisinga first weight for an intermediate inter prediction value of the currentblock and a second weight for an intermediate intra prediction value ofthe current block, wherein the combined inter and intra predictioncoding technique uses a weighted sum of the intermediate interprediction value and the intermediate intra prediction value by usingthe weight pair to derive a prediction value of the current block, andwherein the intra-prediction mode of the current block is determinedwithout referencing an intra-prediction mode of any neighboring block,wherein whether a combined inter and intra prediction process isapplicable to a color component of the current block is determined basedon a color format of the current block, and wherein in response to thecombined inter and intra prediction process being applicable to thecolor component, the intermediate inter prediction value and theintermediate intra prediction value of the color component are used toderive a prediction value of the color component, and wherein a Planarintra prediction mode is used for the current block.
 2. The method ofclaim 1, wherein the neighboring block comprises a block coded using thecombined inter and intra prediction coding technique.
 3. The method ofclaim 1, wherein determining the intra-prediction mode bypasses a MostProbable Modes (MPM) construction process of the current block.
 4. Themethod of claim 1, wherein only a subset of a list of Most ProbableModes (MPMs) for a normal intra coding technique is used for the currentblock.
 5. The method of claim 4, wherein the subset comprises a singleMPM mode in the list of MPM modes for the normal intra coding technique.6. The method of claim 4, wherein the single MPM mode is the first MPMmode in the list.
 7. The method of claim 5, wherein an index indicatingthe single MPM mode is omitted in the bitstream.
 8. The method of claim1, wherein whether the combined inter and intra prediction process isapplicable to the color component of the current block is further basedon a size of the current block.
 9. The method of claim 8, wherein thecolor component comprises a chroma component, and wherein the combinedinter and intra prediction process is not performed to the chromacomponent in case that the color format is 4:2:0 and a width of thecurrent block is equal to or smaller than
 4. 10. The method of claim 8,wherein the color component comprises a chroma component, and whereinthe combined inter and intra prediction process is not performed to thechroma component in case that the color format is 4:2:0 and a height ofthe current block is equal to or smaller than
 4. 11. The method of claim8, wherein the chroma component uses a Planar intra prediction mode. 12.The method of claim 8, wherein the color component comprises a chromacomponent, and wherein the combined inter and intra prediction processis not performed to the chroma component in case that the color formatis 4:4:4 and a width or a height of the current block is smaller than 4.13. The method of claim 1, wherein performing the conversion includesdecoding the current block from the bitstream.
 14. The method of claim1, wherein performing the conversion includes encoding the current blockinto the bitstream.
 15. An apparatus for processing video datacomprising a processor and a non-transitory memory with instructionsthereon, wherein the instructions upon execution by the processor, causethe processor to: determine, for a conversion between a current block ofa video coded using a combined inter and intra prediction codingtechnique and a bitstream of the video, an intra-prediction mode of thecurrent block independently from an intra-prediction mode of aneighboring block; and perform the conversion based on the determining;wherein a weight pair is determined for the current block, and theweight pair comprising a first weight for an intermediate interprediction value of the current block and a second weight for anintermediate intra prediction value of the current block, wherein thecombined inter and intra prediction coding technique uses a weighted sumof the intermediate inter prediction value and the intermediate intraprediction value by using the weight pair to derive a prediction valueof the current block, and wherein the intra-prediction mode of thecurrent block is determined without referencing an intra-prediction modeof any neighboring block, wherein whether a combined inter and intraprediction process is applicable to a color component of the currentblock is determined based on a color format of the current block, andwherein, in response to the combined inter and intra prediction processbeing applicable to the color component, the intermediate interprediction value and the intermediate intra prediction value of thecolor component are used to derive a prediction value of the colorcomponent, and wherein a Planar intra prediction mode is used for thecurrent block.
 16. A non-transitory computer-readable storage mediumstoring instructions that cause a processor to: determine, for aconversion between a current block of a video coded using a combinedinter and intra prediction coding technique and a bitstream of thevideo, an intra-prediction mode of the current block independently froman intra-prediction mode of a neighboring block; and perform theconversion based on the determining; wherein a weight pair is determinedfor the current block, and the weight pair comprising a first weight foran intermediate inter prediction value of the current block and a secondweight for an intermediate intra prediction value of the current block,wherein the combined inter and intra prediction coding technique uses aweighted sum of the intermediate inter prediction value and theintermediate intra prediction value by using the weight pair to derive aprediction value of the current block, and wherein the intra-predictionmode of the current block is determined without referencing anintra-prediction mode of any neighboring block, wherein whether acombined inter and intra prediction process is applicable to a colorcomponent of the current block is determined based on a color format ofthe current block; wherein, in response to the combined inter and intraprediction process being applicable to the color component, theintermediate inter prediction value and the intermediate intraprediction value of the color component to derive a prediction value ofthe color component, and wherein a Planar intra prediction mode is usedfor the current block.
 17. A non-transitory computer-readable recordingmedium storing a bitstream of a video which is generated by a methodperformed by a video processing apparatus, wherein the method comprises:determining, for a current block of a video coded using a combined interand intra prediction coding technique, an intra-prediction mode of thecurrent block independently from an intra-prediction mode of aneighboring block; and generating the bitstream from the current blockbased on the determining; wherein a weight pair is determined for thecurrent block, and the weight pair comprising a first weight for anintermediate inter prediction value of the current block and a secondweight for an intermediate intra prediction value of the current block,wherein the combined inter and intra prediction coding technique uses aweighted sum of the intermediate inter prediction value and theintermediate intra prediction value by using the weight pair to derive aprediction value of the current block, and wherein the intra-predictionmode of the current block is determined without referencing anintra-prediction mode of any neighboring block, wherein whether acombined inter and intra prediction process is applicable to a colorcomponent of the current block is determined based on a color format ofthe current block, and wherein, in response to the combined inter andintra prediction process being applicable to the color component, theintermediate inter prediction value and the intermediate intraprediction value of the color component to derive a prediction value ofthe color component, and wherein a Planar intra prediction mode is usedfor the current block.
 18. The apparatus of claim 15, wherein theneighboring block comprises a block coded using the combined inter andintra prediction coding technique.
 19. The non-transitorycomputer-readable storage medium of claim 16, wherein the neighboringblock comprises a block coded using the combined inter and intraprediction coding technique.